|
源码分析一分析到了parse_loglevel()，继续往下，接下来代码如下：
//argv[1]中包含”-d”，则进入if逻辑，回调log_callback_null函数内容是空的，ffmpeg的指令中也没有单独找到”-d”的选项，都是与”n”结合的，所以，这里的代码是什么意思，没有想明白
if(argc>1 && !strcmp(argv[1], "-d")){
run_as_daemon=1;
av_log_set_callback(log_callback_null);
argc--;
argv++;
}
跳过这一段，继续往下看，代码如下：
#if CONFIG_AVDEVICE
avdevice_register_all();
#endif
avformat_network_init();
//将这种信息显示一遍
show_banner(argc, argv, options);
device注册，网络初始化没什么好讲的，不深入研究，下面看下
show_banner，定义如下：
//banner,翻译中文为横幅的意思
void show_banner(int argc, char **argv, const OptionDef *options)
{
//查找版本参数
int idx = locate_option(argc, argv, options, "version");
if (hide_banner || idx)
return;
//项目信息
print_program_info (INDENT|SHOW_COPYRIGHT, AV_LOG_INFO);
//配置信息
print_all_libs_info(INDENT|SHOW_CONFIG, AV_LOG_INFO);
//版本信息
print_all_libs_info(INDENT|SHOW_VERSION, AV_LOG_INFO);
}
print_program_info定义如下：
static void print_program_info(int flags, int level)
{
const char *indent = flags & INDENT? " " : "";
//program_name代表三种工具的名字，全局变量
av_log(NULL, level, "%s version " FFMPEG_VERSION, program_name);
if (flags & SHOW_COPYRIGHT)
av_log(NULL, level, " Copyright (c) %d-%d the FFmpeg developers",
program_birth_year, CONFIG_THIS_YEAR);
av_log(NULL, level, "\n");
av_log(NULL, level, "%sbuilt with %s\n", indent, CC_IDENT);
av_log(NULL, level, "%sconfiguration: " FFMPEG_CONFIGURATION "\n", indent);
}
继续在main中往下看，代码如下：
/* parse options and open all input/output files */
ret = ffmpeg_parse_options(argc, argv);
if (ret < 0)
exit_program(1);
//输入文件，输出文件的文件句柄，此处判断应该已经都执行了open操作，但是，在哪里open的呢？
if (nb_output_files <= 0 && nb_input_files == 0) {
show_usage();
av_log(NULL, AV_LOG_WARNING, "Use -h to get full help or, even better, run 'man %s'\n", program_name);
exit_program(1);
}
/* file converter / grab */
if (nb_output_files <= 0) {
av_log(NULL, AV_LOG_FATAL, "At least one output file must be specified\n");
exit_program(1);
}
for (i = 0; i < nb_output_files; i++) {
if (strcmp(output_files[i]->ctx->oformat->name, "rtp"))
want_sdp = 0;
}
ffmpeg_parse_options函数是又一个重点.
ffmpeg_parse_options在文件ffmpeg_opt.c中定义如下：
int ffmpeg_parse_options(int argc, char **argv)
{
//通过对OptionParseContext结构体的分析，该结构基本上包含了一个文件的所有配置信息
OptionParseContext octx;
uint8_t error[128];
int ret;
memset(&octx, 0, sizeof(octx));
/* split the commandline into an internal representation */
//翻译：将命令拆分为一个内部表示
//options是源码分析一里面的参数列表
//查看groups定义，分了输入和输出两个组
//split_commandline的工作内容是填充了octx值，同时初始化了4个全局变量，对输入参数进行了合理的参数分配，分配到对应的octx结构中
ret = split_commandline(&octx, argc, argv, options, groups,
FF_ARRAY_ELEMS(groups));
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "Error splitting the argument list: ");
goto fail;
}
/* apply global options */
//申请全局操作?这里不是很清楚
ret = parse_optgroup(NULL, &octx.global_opts);
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "Error parsing global options: ");
goto fail;
}
/* configure terminal and setup signal handlers */
//终端的信号处理等等
term_init();
/* open input files */
ret = open_files(&octx.groups[GROUP_INFILE], "input", open_input_file);
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "Error opening input files: ");
goto fail;
}
/* create the complex filtergraphs */
//创建复杂的过滤器组
ret = init_complex_filters();
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "Error initializing complex filters.\n");
goto fail;
}
/* open output files */
//函数open_files是相同的，不同的作为参数的第三个函数，需要具体分析
//open_output_file函数对输出文件的参数，各个通道的流，指令行参数，都进行了处理填充
ret = open_files(&octx.groups[GROUP_OUTFILE], "output", open_output_file);
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "Error opening output files: ");
goto fail;
}
check_filter_outputs();
fail:
uninit_parse_context(&octx);
if (ret < 0) {
av_strerror(ret, error, sizeof(error));
av_log(NULL, AV_LOG_FATAL, "%s\n", error);
}
return ret;
}
先来看下OptionParseContext结构体内容
OptionParseContext定义如下：
typedef struct OptionParseContext {
//全局的操作组？先这样理解吧
OptionGroup global_opts;
//组列表
OptionGroupList *groups;
//猜测是组的类型
int nb_groups;
//
/* parsing state */
OptionGroup cur_group;
} OptionParseContext;
OptionGroup定义如下：
typedef struct OptionGroup {
const OptionGroupDef *group_def;
const char *arg;
Option *opts;
int nb_opts;
//AVDictionary 是定义的map工具，存储健值对
AVDictionary *codec_opts;
AVDictionary *format_opts;
//重新取样参数健值对
AVDictionary *resample_opts;
//视频采样选项健值对
AVDictionary *sws_dict;
//音频采样选项健值对
AVDictionary *swr_opts;
} OptionGroup;
OptionGroupList定义如下：
/**
* A list of option groups that all have the same group type
* (e.g. input files or output files)
*/
//这里有解释：具有相同的组类型的组列表，例如输入文件和输出文件
//这里输入如文件和输出文件归为相同的组，是什么依据因素？先搁置
typedef struct OptionGroupList {
const OptionGroupDef *group_def;
OptionGroup *groups;
int nb_groups;
} OptionGroupList;
OptionGroupDef定义如下：
typedef struct OptionGroupDef {
/**< group name */
const char *name;
/**
* Option to be used as group separator. Can be NULL for groups which
* are terminated by a non-option argument (e.g. ffmpeg output files)
*/
//组分隔符？没懂
const char *sep;
/**
* Option flags that must be set on each option that is
* applied to this group
*/
//必须为组设置标志，也就是该值必须被设置
int flags;
} OptionGroupDef;
split_commandline定义如下：
int split_commandline(OptionParseContext *octx, int argc, char *argv[],
const OptionDef *options,
const OptionGroupDef *groups, int nb_groups)
{
int optindex = 1;
int dashdash = -2;
/* perform system-dependent conversions for arguments list */
//对参数列表执行系统依赖的转换
//对于linux，该函数没有做任何处理
prepare_app_arguments(&argc, &argv);
//填充了octx的值，并且设置了sws_dict的flags值
init_parse_context(octx, groups, nb_groups);
av_log(NULL, AV_LOG_DEBUG, "Splitting the commandline.\n");
while (optindex < argc) {
const char *opt = argv[optindex++], *arg;
const OptionDef *po;
int ret;
av_log(NULL, AV_LOG_DEBUG, "Reading option '%s' ...", opt);
//只有--的情况
if (opt[0] == '-' && opt[1] == '-' && !opt[2]) {
dashdash = optindex;
continue;
}
/* unnamed group separators, e.g. output filename */
//没有带标志（-xx）的参数情况
if (opt[0] != '-' || !opt[1] || dashdash+1 == optindex) {
finish_group(octx, 0, opt);
av_log(NULL, AV_LOG_DEBUG, " matched as %s.\n", groups[0].name);
continue;
}
opt++;
//此处定义了，在下面会用到，作用是获取下一个参数
#define GET_ARG(arg) \
do { \
arg = argv[optindex++]; \
if (!arg) { \
av_log(NULL, AV_LOG_ERROR, "Missing argument for option '%s'.\n", opt);\
return AVERROR(EINVAL); \
} \
} while (0)
/* named group separators, e.g. -i */
//名字组分隔
//找出参数是属于输入组还是输出组，返回的ret代表
if ((ret = match_group_separator(groups, nb_groups, opt)) >= 0) {
GET_ARG(arg);
finish_group(octx, ret, arg);
av_log(NULL, AV_LOG_DEBUG, " matched as %s with argument '%s'.\n",
groups[ret].name, arg);
continue;
}
/* normal options */
//寻找出带：的参数
po = find_option(options, opt);
if (po->name) {
if (po->flags & OPT_EXIT) {
/* optional argument, e.g. -h */
arg = argv[optindex++];
} else if (po->flags & HAS_ARG) {
GET_ARG(arg);
} else {
arg = "1";
}
//将po，opt，arg数据填入octx中
add_opt(octx, po, opt, arg);
av_log(NULL, AV_LOG_DEBUG, " matched as option '%s' (%s) with "
"argument '%s'.\n", po->name, po->help, arg);
continue;
}
/* AVOptions */
if (argv[optindex]) {
//对codec_opts，format_opts，sws_dict，swr_opts四个全局变量进行初始化，参数配置
ret = opt_default(NULL, opt, argv[optindex]);
if (ret >= 0) {
av_log(NULL, AV_LOG_DEBUG, " matched as AVOption '%s' with "
"argument '%s'.\n", opt, argv[optindex]);
optindex++;
continue;
} else if (ret != AVERROR_OPTION_NOT_FOUND) {
av_log(NULL, AV_LOG_ERROR, "Error parsing option '%s' "
"with argument '%s'.\n", opt, argv[optindex]);
return ret;
}
}
/* boolean -nofoo options */
//处理-no 选项，但是问题是，我在ffmpeg -help指令中没有看到有no的选项啊？？？
if (opt[0] == 'n' && opt[1] == 'o' &&
(po = find_option(options, opt + 2)) &&
po->name && po->flags & OPT_BOOL) {
add_opt(octx, po, opt, "0");
av_log(NULL, AV_LOG_DEBUG, " matched as option '%s' (%s) with "
"argument 0.\n", po->name, po->help);
continue;
}
av_log(NULL, AV_LOG_ERROR, "Unrecognized option '%s'.\n", opt);
return AVERROR_OPTION_NOT_FOUND;
}
if (octx->cur_group.nb_opts || codec_opts || format_opts || resample_opts)
av_log(NULL, AV_LOG_WARNING, "Trailing option(s) found in the "
"command: may be ignored.\n");
av_log(NULL, AV_LOG_DEBUG, "Finished splitting the commandline.\n");
return 0;
}
prepare_app_arguments定义如下：
//这里有平台差异，因为我是运行在linux上的，所以，else分支内容就是不需要特殊处理
//对于win平台做的工作大概内容是字符转换，utf-8字符转换处理等
static inline void prepare_app_arguments(int *argc_ptr, char ***argv_ptr)
{
/* nothing to do */
}
init_parse_context定义如下：
static void init_parse_context(OptionParseContext *octx,
const OptionGroupDef *groups, int nb_groups)
{
static const OptionGroupDef global_group = { "global" };
int i;
memset(octx, 0, sizeof(*octx));
//将groups，groups内容填充到octx对应的结构中
octx->nb_groups = nb_groups;
octx->groups = av_mallocz_array(octx->nb_groups, sizeof(*octx->groups));
if (!octx->groups)
exit_program(1);
for (i = 0; i < octx->nb_groups; i++)
octx->groups[i].group_def = &groups[i];
octx->global_opts.group_def = &global_group;
octx->global_opts.arg = "";
//设置sws_dict的flags值
init_opts();
}
init_opts定义如下：
void init_opts(void)
{
av_dict_set(&sws_dict, "flags", "bicubic", 0);
}
match_group_separator定义如下：
/*
* Check whether given option is a group separator.
*
* @return index of the group definition that matched or -1 if none
*/
//查找出这个opt是那一组的，返回组编号，nb_groups是组个数
static int match_group_separator(const OptionGroupDef *groups, int nb_groups,
const char *opt)
{
int i;
for (i = 0; i < nb_groups; i++) {
const OptionGroupDef *p = &groups[i];
if (p->sep && !strcmp(p->sep, opt))
return i;
}
return -1;
}
opt_default定义如下：
#define FLAGS (o->type == AV_OPT_TYPE_FLAGS && (arg[0]=='-' || arg[0]=='+')) ? AV_DICT_APPEND : 0
//opt_default的主要工作就是对codec_opts，format_opts，sws_dict，swr_opts四个全局变量进行初始化，参数配置，调用av_dict_set完成
int opt_default(void *optctx, const char *opt, const char *arg)
{
const AVOption *o;
int consumed = 0;
char opt_stripped[128];
const char *p;
//分别创建了编解码，格式，视频转换，音频转换的类
const AVClass *cc = avcodec_get_class(), *fc = avformat_get_class();
#if CONFIG_SWSCALE
const AVClass *sc = sws_get_class();
#endif
#if CONFIG_SWRESAMPLE
const AVClass *swr_class = swr_get_class();
#endif
//如果是debug模式，相应日志也设为debug模式
if (!strcmp(opt, "debug") || !strcmp(opt, "fdebug"))
av_log_set_level(AV_LOG_DEBUG);
//查找：出现的位置
if (!(p = strchr(opt, ':')))
p = opt + strlen(opt);
//封装了一层字符串复制功能
av_strlcpy(opt_stripped, opt, FFMIN(sizeof(opt_stripped), p - opt + 1));
//这里的opt_find不可以和源码一中的find_opt弄混了，是两个函数
//opt_find函数的功能是在cc中找到 opt_stripped的参数名
//在cc中找到 opt_stripped的参数名或者，v，a，s和其对应的参数
if ((o = opt_find(&cc, opt_stripped, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ)) ||
((opt[0] == 'v' || opt[0] == 'a' || opt[0] == 's') &&
(o = opt_find(&cc, opt + 1, NULL, 0, AV_OPT_SEARCH_FAKE_OBJ)))) {
av_dict_set(&codec_opts, opt, arg, FLAGS);
consumed = 1;
}
if ((o = opt_find(&fc, opt, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ))) {
av_dict_set(&format_opts, opt, arg, FLAGS);
if (consumed)
av_log(NULL, AV_LOG_VERBOSE, "Routing option %s to both codec and muxer layer\n", opt);
consumed = 1;
}
#if CONFIG_SWSCALE
if (!consumed && (o = opt_find(&sc, opt, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ))) {
struct SwsContext *sws = sws_alloc_context();
int ret = av_opt_set(sws, opt, arg, 0);
sws_freeContext(sws);
if (!strcmp(opt, "srcw") || !strcmp(opt, "srch") ||
!strcmp(opt, "dstw") || !strcmp(opt, "dsth") ||
!strcmp(opt, "src_format") || !strcmp(opt, "dst_format")) {
av_log(NULL, AV_LOG_ERROR, "Directly using swscale dimensions/format options is not supported, please use the -s or -pix_fmt options\n");
return AVERROR(EINVAL);
}
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error setting option %s.\n", opt);
return ret;
}
av_dict_set(&sws_dict, opt, arg, FLAGS);
consumed = 1;
}
#else
if (!consumed && !strcmp(opt, "sws_flags")) {
av_log(NULL, AV_LOG_WARNING, "Ignoring %s %s, due to disabled swscale\n", opt, arg);
consumed = 1;
}
#endif
#if CONFIG_SWRESAMPLE
if (!consumed && (o=opt_find(&swr_class, opt, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ))) {
struct SwrContext *swr = swr_alloc();
int ret = av_opt_set(swr, opt, arg, 0);
swr_free(&swr);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error setting option %s.\n", opt);
return ret;
}
av_dict_set(&swr_opts, opt, arg, FLAGS);
consumed = 1;
}
#endif
if (consumed)
return 0;
return AVERROR_OPTION_NOT_FOUND;
}
opt_find定义如下：
//在obj中找到对饮的name的AVOption 结构
static const AVOption *opt_find(void *obj, const char *name, const char *unit,
int opt_flags, int search_flags)
{
const AVOption *o = av_opt_find(obj, name, unit, opt_flags, search_flags);
if(o && !o->flags)
return NULL;
return o;
}
av_opt_find 和av_opt_find2的定义如下：
const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
int opt_flags, int search_flags)
{
return av_opt_find2(obj, name, unit, opt_flags, search_flags, NULL);
}
const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
int opt_flags, int search_flags, void **target_obj)
{
const AVClass *c;
const AVOption *o = NULL;
if(!obj)
return NULL;
c= *(AVClass**)obj;
if (!c)
return NULL;
if (search_flags & AV_OPT_SEARCH_CHILDREN) {
if (search_flags & AV_OPT_SEARCH_FAKE_OBJ) {
void *iter = NULL;
const AVClass *child;
while (child = av_opt_child_class_iterate(c, &iter))
//递归调用
if (o = av_opt_find2(&child, name, unit, opt_flags, search_flags, NULL))
return o;
} else {
void *child = NULL;
while (child = av_opt_child_next(obj, child))
if (o = av_opt_find2(child, name, unit, opt_flags, search_flags, target_obj))
return o;
}
}
while (o = av_opt_next(obj, o)) {
if (!strcmp(o->name, name) && (o->flags & opt_flags) == opt_flags &&
((!unit && o->type != AV_OPT_TYPE_CONST) ||
(unit && o->type == AV_OPT_TYPE_CONST && o->unit && !strcmp(o->unit, unit)))) {
if (target_obj) {
if (!(search_flags & AV_OPT_SEARCH_FAKE_OBJ))
*target_obj = obj;
else
*target_obj = NULL;
}
return o;
}
}
return NULL;
}
parse_optgroup定义如下：
int parse_optgroup(void *optctx, OptionGroup *g)
{
int i, ret;
av_log(NULL, AV_LOG_DEBUG, "Parsing a group of options: %s %s.\n",
g->group_def->name, g->arg);
for (i = 0; i < g->nb_opts; i++) {
Option *o = &g->opts[i];
if (g->group_def->flags &&
!(g->group_def->flags & o->opt->flags)) {
av_log(NULL, AV_LOG_ERROR, "Option %s (%s) cannot be applied to "
"%s %s -- you are trying to apply an input option to an "
"output file or vice versa. Move this option before the "
"file it belongs to.\n", o->key, o->opt->help,
g->group_def->name, g->arg);
return AVERROR(EINVAL);
}
av_log(NULL, AV_LOG_DEBUG, "Applying option %s (%s) with argument %s.\n",
o->key, o->opt->help, o->val);
//取optctx对o->opt, o->key, o->val进行填充？这里我有一点疑问？是这样的的填充吗？
ret = write_option(optctx, o->opt, o->key, o->val);
if (ret < 0)
return ret;
}
av_log(NULL, AV_LOG_DEBUG, "Successfully parsed a group of options.\n");
return 0;
}
write_option定义如下：
static int write_option(void *optctx, const OptionDef *po, const char *opt,
const char *arg)
{
/* new-style options contain an offset into optctx, old-style address of
* a global var*/
//新样式的选项包含到optctx的偏移量，全局变量的旧样式地址
//取出po中的偏移量
void *dst = po->flags & (OPT_OFFSET | OPT_SPEC) ?
(uint8_t *)optctx + po->u.off : po->u.dst_ptr;
int *dstcount;
if (po->flags & OPT_SPEC) {
SpecifierOpt **so = dst;
//p取的是：之后的参数，例如c：s，p指向s
char *p = strchr(opt, ':');
char *str;
dstcount = (int *)(so + 1);
//判断so的空间是否够用，不够的重新申请足够的空间给so，并完成初始化
*so = grow_array(*so, sizeof(**so), dstcount, *dstcount + 1);
//p是否有值，有值的话申请值大小的内存空间
str = av_strdup(p ? p + 1 : "");
if (!str)
return AVERROR(ENOMEM);
(*so)[*dstcount - 1].specifier = str;
//这里将dst指向so的地址，完成从optctx中取值
dst = &(*so)[*dstcount - 1].u;
}
if (po->flags & OPT_STRING) {
char *str;
str = av_strdup(arg);
av_freep(dst);
if (!str)
return AVERROR(ENOMEM);
*(char **)dst = str;
} else if (po->flags & OPT_BOOL || po->flags & OPT_INT) {
*(int *)dst = parse_number_or_die(opt, arg, OPT_INT64, INT_MIN, INT_MAX);
} else if (po->flags & OPT_INT64) {
*(int64_t *)dst = parse_number_or_die(opt, arg, OPT_INT64, INT64_MIN, INT64_MAX);
} else if (po->flags & OPT_TIME) {
*(int64_t *)dst = parse_time_or_die(opt, arg, 1);
} else if (po->flags & OPT_FLOAT) {
*(float *)dst = parse_number_or_die(opt, arg, OPT_FLOAT, -INFINITY, INFINITY);
} else if (po->flags & OPT_DOUBLE) {
*(double *)dst = parse_number_or_die(opt, arg, OPT_DOUBLE, -INFINITY, INFINITY);
} else if (po->u.func_arg) {
//这里指向了结构体func_arg函数
int ret = po->u.func_arg(optctx, opt, arg);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR,
"Failed to set value '%s' for option '%s': %s\n",
arg, opt, av_err2str(ret));
return ret;
}
}
if (po->flags & OPT_EXIT)
exit_program(0);
return 0;
}
parse_number_or_die定义如下：
double parse_number_or_die(const char *context, const char *numstr, int type,
double min, double max)
{
char *tail;
const char *error;
//av_strtod函数是将字符串转成double
double d = av_strtod(numstr, &tail);
if (*tail)
error = "Expected number for %s but found: %s\n";
else if (d < min || d > max)
error = "The value for %s was %s which is not within %f - %f\n";
else if (type == OPT_INT64 && (int64_t)d != d)
error = "Expected int64 for %s but found %s\n";
else if (type == OPT_INT && (int)d != d)
error = "Expected int for %s but found %s\n";
else
return d;
av_log(NULL, AV_LOG_FATAL, error, context, numstr, min, max);
exit_program(1);
return 0;
}
open_input_file定义如下：
//该函数在整个ffmpeg的项目中有多处定义，分别在不同的文件中，该定义在ffmpeg_opt.c中的定义
//参数OptionsContext 是定义操作的上下文，猜测在前面的步骤已经填充乐一部分相关的选项进去，此函数中会再次进行详细的填充，和取值所用
static int open_input_file(OptionsContext *o, const char *filename)
{
InputFile *f;
AVFormatContext *ic;
AVInputFormat *file_iformat = NULL;
int err, i, ret;
int64_t timestamp;
AVDictionary *unused_opts = NULL;
AVDictionaryEntry *e = NULL;
char * video_codec_name = NULL;
char * audio_codec_name = NULL;
char *subtitle_codec_name = NULL;
char * data_codec_name = NULL;
int scan_all_pmts_set = 0;
if (o->stop_time != INT64_MAX && o->recording_time != INT64_MAX) {
o->stop_time = INT64_MAX;
av_log(NULL, AV_LOG_WARNING, "-t and -to cannot be used together; using -t.\n");
}
if (o->stop_time != INT64_MAX && o->recording_time == INT64_MAX) {
int64_t start_time = o->start_time == AV_NOPTS_VALUE ? 0 : o->start_time;
if (o->stop_time <= start_time) {
av_log(NULL, AV_LOG_ERROR, "-to value smaller than -ss; aborting.\n");
exit_program(1);
} else {
o->recording_time = o->stop_time - start_time;
}
}
if (o->format) {
if (!(file_iformat = av_find_input_format(o->format))) {
av_log(NULL, AV_LOG_FATAL, "Unknown input format: '%s'\n", o->format);
exit_program(1);
}
}
//上面三个if就是对o的取值判断，值是否符合规则
//这里为什么要去匹配”-”？？？
if (!strcmp(filename, "-"))
filename = "pipe:";
//这里创建输出到终端的文件
stdin_interaction &= strncmp(filename, "pipe:", 5) &&
strcmp(filename, "/dev/stdin");
/* get default parameters from command line */
ic = avformat_alloc_context();
if (!ic) {
print_error(filename, AVERROR(ENOMEM));
exit_program(1);
}
if (o->nb_audio_sample_rate) {
av_dict_set_int(&o->g->format_opts, "sample_rate", o->audio_sample_rate[o->nb_audio_sample_rate - 1].u.i, 0);
}
if (o->nb_audio_channels) {
/* because we set audio_channels based on both the "ac" and
* "channel_layout" options, we need to check that the specified
* demuxer actually has the "channels" option before setting it */
if (file_iformat && file_iformat->priv_class &&
av_opt_find(&file_iformat->priv_class, "channels", NULL, 0,
AV_OPT_SEARCH_FAKE_OBJ)) {
av_dict_set_int(&o->g->format_opts, "channels", o->audio_channels[o->nb_audio_channels - 1].u.i, 0);
}
}
if (o->nb_frame_rates) {
/* set the format-level framerate option;
* this is important for video grabbers, e.g. x11 */
if (file_iformat && file_iformat->priv_class &&
av_opt_find(&file_iformat->priv_class, "framerate", NULL, 0,
AV_OPT_SEARCH_FAKE_OBJ)) {
av_dict_set(&o->g->format_opts, "framerate",
o->frame_rates[o->nb_frame_rates - 1].u.str, 0);
}
}
if (o->nb_frame_sizes) {
av_dict_set(&o->g->format_opts, "video_size", o->frame_sizes[o->nb_frame_sizes - 1].u.str, 0);
}
if (o->nb_frame_pix_fmts)
av_dict_set(&o->g->format_opts, "pixel_format", o->frame_pix_fmts[o->nb_frame_pix_fmts - 1].u.str, 0);
//通过宏定义的定义，获取code_name的值
MATCH_PER_TYPE_OPT(codec_names, str, video_codec_name, ic, "v");
MATCH_PER_TYPE_OPT(codec_names, str, audio_codec_name, ic, "a");
MATCH_PER_TYPE_OPT(codec_names, str, subtitle_codec_name, ic, "s");
MATCH_PER_TYPE_OPT(codec_names, str, data_codec_name, ic, "d");
//通过第四个参数0，确认是哪一种数据流的解码器
if (video_codec_name)
ic->video_codec = find_codec_or_die(video_codec_name , AVMEDIA_TYPE_VIDEO , 0);
if (audio_codec_name)
ic->audio_codec = find_codec_or_die(audio_codec_name , AVMEDIA_TYPE_AUDIO , 0);
if (subtitle_codec_name)
ic->subtitle_codec = find_codec_or_die(subtitle_codec_name, AVMEDIA_TYPE_SUBTITLE, 0);
if (data_codec_name)
ic->data_codec = find_codec_or_die(data_codec_name , AVMEDIA_TYPE_DATA , 0);
//AVCodeID赋值
ic->video_codec_id = video_codec_name ? ic->video_codec->id : AV_CODEC_ID_NONE;
ic->audio_codec_id = audio_codec_name ? ic->audio_codec->id : AV_CODEC_ID_NONE;
ic->subtitle_codec_id = subtitle_codec_name ? ic->subtitle_codec->id : AV_CODEC_ID_NONE;
ic->data_codec_id = data_codec_name ? ic->data_codec->id : AV_CODEC_ID_NONE;
ic->flags |= AVFMT_FLAG_NONBLOCK;
if (o->bitexact)
ic->flags |= AVFMT_FLAG_BITEXACT;
//解码的回调函数调用
ic->interrupt_callback = int_cb;
if (!av_dict_get(o->g->format_opts, "scan_all_pmts", NULL, AV_DICT_MATCH_CASE)) {
av_dict_set(&o->g->format_opts, "scan_all_pmts", "1", AV_DICT_DONT_OVERWRITE);
scan_all_pmts_set = 1;
}
/* open the input file with generic avformat function */
err = avformat_open_input(&ic, filename, file_iformat, &o->g->format_opts);
if (err < 0) {
print_error(filename, err);
if (err == AVERROR_PROTOCOL_NOT_FOUND)
av_log(NULL, AV_LOG_ERROR, "Did you mean file:%s?\n", filename);
exit_program(1);
}
if (scan_all_pmts_set)
av_dict_set(&o->g->format_opts, "scan_all_pmts", NULL, AV_DICT_MATCH_CASE);
//重置两个参数
remove_avoptions(&o->g->format_opts, o->g->codec_opts);
assert_avoptions(o->g->format_opts);
/* apply forced codec ids */
for (i = 0; i < ic->nb_streams; i++)
choose_decoder(o, ic, ic->streams[i]);
//下面是一些参数，数据的判定
if (find_stream_info) {
AVDictionary **opts = setup_find_stream_info_opts(ic, o->g->codec_opts);
int orig_nb_streams = ic->nb_streams;
/* If not enough info to get the stream parameters, we decode the
first frames to get it. (used in mpeg case for example) */
ret = avformat_find_stream_info(ic, opts);
for (i = 0; i < orig_nb_streams; i++)
av_dict_free(&opts[i]);
av_freep(&opts);
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "%s: could not find codec parameters\n", filename);
if (ic->nb_streams == 0) {
avformat_close_input(&ic);
exit_program(1);
}
}
}
if (o->start_time != AV_NOPTS_VALUE && o->start_time_eof != AV_NOPTS_VALUE) {
av_log(NULL, AV_LOG_WARNING, "Cannot use -ss and -sseof both, using -ss for %s\n", filename);
o->start_time_eof = AV_NOPTS_VALUE;
}
if (o->start_time_eof != AV_NOPTS_VALUE) {
if (o->start_time_eof >= 0) {
av_log(NULL, AV_LOG_ERROR, "-sseof value must be negative; aborting\n");
exit_program(1);
}
if (ic->duration > 0) {
o->start_time = o->start_time_eof + ic->duration;
if (o->start_time < 0) {
av_log(NULL, AV_LOG_WARNING, "-sseof value seeks to before start of file %s; ignored\n", filename);
o->start_time = AV_NOPTS_VALUE;
}
} else
av_log(NULL, AV_LOG_WARNING, "Cannot use -sseof, duration of %s not known\n", filename);
}
timestamp = (o->start_time == AV_NOPTS_VALUE) ? 0 : o->start_time;
/* add the stream start time */
if (!o->seek_timestamp && ic->start_time != AV_NOPTS_VALUE)
timestamp += ic->start_time;
/* if seeking requested, we execute it */
if (o->start_time != AV_NOPTS_VALUE) {
int64_t seek_timestamp = timestamp;
if (!(ic->iformat->flags & AVFMT_SEEK_TO_PTS)) {
int dts_heuristic = 0;
for (i=0; i<ic->nb_streams; i++) {
const AVCodecParameters *par = ic->streams[i]->codecpar;
if (par->video_delay) {
dts_heuristic = 1;
break;
}
}
if (dts_heuristic) {
seek_timestamp -= 3*AV_TIME_BASE / 23;
}
}
ret = avformat_seek_file(ic, -1, INT64_MIN, seek_timestamp, seek_timestamp, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_WARNING, "%s: could not seek to position %0.3f\n",
filename, (double)timestamp / AV_TIME_BASE);
}
}
/* update the current parameters so that they match the one of the input stream */
//将文件的数据流参数拷贝到上文结构中
add_input_streams(o, ic);
/* dump the file content */
av_dump_format(ic, nb_input_files, filename, 0);
//输入文件的数据流内存申请
GROW_ARRAY(input_files, nb_input_files);
f = av_mallocz(sizeof(*f));
if (!f)
exit_program(1);
input_files[nb_input_files - 1] = f;
//数据填充
f->ctx = ic;
f->ist_index = nb_input_streams - ic->nb_streams;
f->start_time = o->start_time;
f->recording_time = o->recording_time;
f->input_ts_offset = o->input_ts_offset;
f->ts_offset = o->input_ts_offset - (copy_ts ? (start_at_zero && ic->start_time != AV_NOPTS_VALUE ? ic->start_time : 0) : timestamp);
f->nb_streams = ic->nb_streams;
f->rate_emu = o->rate_emu;
f->accurate_seek = o->accurate_seek;
f->loop = o->loop;
f->duration = 0;
f->time_base = (AVRational){ 1, 1 };
#if HAVE_THREADS
f->thread_queue_size = o->thread_queue_size > 0 ? o->thread_queue_size : 8;
#endif
/* check if all codec options have been used */
unused_opts = strip_specifiers(o->g->codec_opts);
for (i = f->ist_index; i < nb_input_streams; i++) {
e = NULL;
while ((e = av_dict_get(input_streams[i]->decoder_opts, "", e,
AV_DICT_IGNORE_SUFFIX)))
av_dict_set(&unused_opts, e->key, NULL, 0);
}
e = NULL;
while ((e = av_dict_get(unused_opts, "", e, AV_DICT_IGNORE_SUFFIX))) {
const AVClass *class = avcodec_get_class();
const AVOption *option = av_opt_find(&class, e->key, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ);
const AVClass *fclass = avformat_get_class();
const AVOption *foption = av_opt_find(&fclass, e->key, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ);
if (!option || foption)
continue;
if (!(option->flags & AV_OPT_FLAG_DECODING_PARAM)) {
av_log(NULL, AV_LOG_ERROR, "Codec AVOption %s (%s) specified for "
"input file #%d (%s) is not a decoding option.\n", e->key,
option->help ? option->help : "", nb_input_files - 1,
filename);
exit_program(1);
}
av_log(NULL, AV_LOG_WARNING, "Codec AVOption %s (%s) specified for "
"input file #%d (%s) has not been used for any stream. The most "
"likely reason is either wrong type (e.g. a video option with "
"no video streams) or that it is a private option of some decoder "
"which was not actually used for any stream.\n", e->key,
option->help ? option->help : "", nb_input_files - 1, filename);
}
av_dict_free(&unused_opts);
for (i = 0; i < o->nb_dump_attachment; i++) {
int j;
for (j = 0; j < ic->nb_streams; j++) {
AVStream *st = ic->streams[j];
if (check_stream_specifier(ic, st, o->dump_attachment[i].specifier) == 1)
dump_attachment(st, o->dump_attachment[i].u.str);
}
}
input_stream_potentially_available = 1;
return 0;
}
open_files定义如下：
//函数功能就是初始化了一遍参数，然后进行了检查，对参数进行了填充，调用第三个参数的回调
static int open_files(OptionGroupList *l, const char *inout,
int (*open_file)(OptionsContext*, const char*))
{
int i, ret;
//这个打开文件书哪一种流，输入组还是输出组，在调用该函数之前已经确定，设置好了
for (i = 0; i < l->nb_groups; i++) {
OptionGroup *g = &l->groups[i];
OptionsContext o;
init_options(&o);
o.g = g;
ret = parse_optgroup(&o, g);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error parsing options for %s file "
"%s.\n", inout, g->arg);
uninit_options(&o);
return ret;
}
av_log(NULL, AV_LOG_DEBUG, "Opening an %s file: %s.\n", inout, g->arg);
//调用第三个参数的函数
ret = open_file(&o, g->arg);
uninit_options(&o);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error opening %s file %s.\n",
inout, g->arg);
return ret;
}
av_log(NULL, AV_LOG_DEBUG, "Successfully opened the file.\n");
}
return 0;
}
open_output_file在ffmpeg_opt.c中定义如下：
static int open_output_file(OptionsContext *o, const char *filename)
{
AVFormatContext *oc;
int i, j, err;
OutputFile *of;
OutputStream *ost;
InputStream *ist;
AVDictionary *unused_opts = NULL;
AVDictionaryEntry *e = NULL;
int format_flags = 0;
if (o->stop_time != INT64_MAX && o->recording_time != INT64_MAX) {
o->stop_time = INT64_MAX;
av_log(NULL, AV_LOG_WARNING, "-t and -to cannot be used together; using -t.\n");
}
if (o->stop_time != INT64_MAX && o->recording_time == INT64_MAX) {
int64_t start_time = o->start_time == AV_NOPTS_VALUE ? 0 : o->start_time;
if (o->stop_time <= start_time) {
av_log(NULL, AV_LOG_ERROR, "-to value smaller than -ss; aborting.\n");
exit_program(1);
} else {
o->recording_time = o->stop_time - start_time;
}
}
GROW_ARRAY(output_files, nb_output_files);
of = av_mallocz(sizeof(*of));
if (!of)
exit_program(1);
output_files[nb_output_files - 1] = of;
of->ost_index = nb_output_streams;
of->recording_time = o->recording_time;
of->start_time = o->start_time;
of->limit_filesize = o->limit_filesize;
of->shortest = o->shortest;
av_dict_copy(&of->opts, o->g->format_opts, 0);
if (!strcmp(filename, "-"))
filename = "pipe:";
err = avformat_alloc_output_context2(&oc, NULL, o->format, filename);
if (!oc) {
print_error(filename, err);
exit_program(1);
}
of->ctx = oc;
if (o->recording_time != INT64_MAX)
oc->duration = o->recording_time;
oc->interrupt_callback = int_cb;
e = av_dict_get(o->g->format_opts, "fflags", NULL, 0);
if (e) {
const AVOption *o = av_opt_find(oc, "fflags", NULL, 0, 0);
av_opt_eval_flags(oc, o, e->value, &format_flags);
}
if (o->bitexact) {
format_flags |= AVFMT_FLAG_BITEXACT;
oc->flags |= AVFMT_FLAG_BITEXACT;
}
//到此处为止，上面的代码还是一些参数赋值，上下文结构申请
//下面就是针对视频流，音频流的单独处理
/* create streams for all unlabeled output pads */
for (i = 0; i < nb_filtergraphs; i++) {
FilterGraph *fg = filtergraphs[i];
for (j = 0; j < fg->nb_outputs; j++) {
OutputFilter *ofilter = fg->outputs[j];
if (!ofilter->out_tmp || ofilter->out_tmp->name)
continue;
switch (ofilter->type) {
case AVMEDIA_TYPE_VIDEO: o->video_disable = 1; break;
case AVMEDIA_TYPE_AUDIO: o->audio_disable = 1; break;
case AVMEDIA_TYPE_SUBTITLE: o->subtitle_disable = 1; break;
}
//输出过滤器初始化
init_output_filter(ofilter, o, oc);
}
}
if (!o->nb_stream_maps) {
char *subtitle_codec_name = NULL;
/* pick the "best" stream of each type */
/* video: highest resolution */
//av_guess_codec函数确定解码器使用哪一种
if (!o->video_disable && av_guess_codec(oc->oformat, NULL, filename, NULL, AVMEDIA_TYPE_VIDEO) != AV_CODEC_ID_NONE) {
int best_score = 0, idx = -1;
int qcr = avformat_query_codec(oc->oformat, oc->oformat->video_codec, 0);
for (i = 0; i < nb_input_streams; i++) {
int score;
ist = input_streams[i];
score = ist->st->codecpar->width * ist->st->codecpar->height
+ 100000000 * !!(ist->st->event_flags & AVSTREAM_EVENT_FLAG_NEW_PACKETS)
+ 5000000*!!(ist->st->disposition & AV_DISPOSITION_DEFAULT);
if (ist->user_set_discard == AVDISCARD_ALL)
continue;
if((qcr!=MKTAG('A', 'P', 'I', 'C')) && (ist->st->disposition & AV_DISPOSITION_ATTACHED_PIC))
score = 1;
if (ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
score > best_score) {
if((qcr==MKTAG('A', 'P', 'I', 'C')) && !(ist->st->disposition & AV_DISPOSITION_ATTACHED_PIC))
continue;
best_score = score;
idx = i;
}
}
if (idx >= 0)
new_video_stream(o, oc, idx);
}
/* audio: most channels */
if (!o->audio_disable && av_guess_codec(oc->oformat, NULL, filename, NULL, AVMEDIA_TYPE_AUDIO) != AV_CODEC_ID_NONE) {
int best_score = 0, idx = -1;
for (i = 0; i < nb_input_streams; i++) {
int score;
ist = input_streams[i];
score = ist->st->codecpar->channels
+ 100000000 * !!(ist->st->event_flags & AVSTREAM_EVENT_FLAG_NEW_PACKETS)
+ 5000000*!!(ist->st->disposition & AV_DISPOSITION_DEFAULT);
if (ist->user_set_discard == AVDISCARD_ALL)
continue;
if (ist->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO &&
score > best_score) {
best_score = score;
idx = i;
}
}
if (idx >= 0)
new_audio_stream(o, oc, idx);
}
/* subtitles: pick first */
MATCH_PER_TYPE_OPT(codec_names, str, subtitle_codec_name, oc, "s");
if (!o->subtitle_disable && (avcodec_find_encoder(oc->oformat->subtitle_codec) || subtitle_codec_name)) {
for (i = 0; i < nb_input_streams; i++)
if (input_streams[i]->st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE) {
AVCodecDescriptor const *input_descriptor =
avcodec_descriptor_get(input_streams[i]->st->codecpar->codec_id);
AVCodecDescriptor const *output_descriptor = NULL;
AVCodec const *output_codec =
avcodec_find_encoder(oc->oformat->subtitle_codec);
int input_props = 0, output_props = 0;
if (input_streams[i]->user_set_discard == AVDISCARD_ALL)
continue;
if (output_codec)
output_descriptor = avcodec_descriptor_get(output_codec->id);
if (input_descriptor)
input_props = input_descriptor->props & (AV_CODEC_PROP_TEXT_SUB | AV_CODEC_PROP_BITMAP_SUB);
if (output_descriptor)
output_props = output_descriptor->props & (AV_CODEC_PROP_TEXT_SUB | AV_CODEC_PROP_BITMAP_SUB);
if (subtitle_codec_name ||
input_props & output_props ||
// Map dvb teletext which has neither property to any output subtitle encoder
input_descriptor && output_descriptor &&
(!input_descriptor->props ||
!output_descriptor->props)) {
new_subtitle_stream(o, oc, i);
break;
}
}
}
/* Data only if codec id match */
//仅当编码器id匹配时的数据
if (!o->data_disable ) {
enum AVCodecID codec_id = av_guess_codec(oc->oformat, NULL, filename, NULL, AVMEDIA_TYPE_DATA);
for (i = 0; codec_id != AV_CODEC_ID_NONE && i < nb_input_streams; i++) {
if (input_streams[i]->user_set_discard == AVDISCARD_ALL)
continue;
if (input_streams[i]->st->codecpar->codec_type == AVMEDIA_TYPE_DATA
&& input_streams[i]->st->codecpar->codec_id == codec_id )
new_data_stream(o, oc, i);
}
}
} else {
//处理输出流
for (i = 0; i < o->nb_stream_maps; i++) {
StreamMap *map = &o->stream_maps[i];
if (map->disabled)
continue;
if (map->linklabel) {
FilterGraph *fg;
OutputFilter *ofilter = NULL;
int j, k;
for (j = 0; j < nb_filtergraphs; j++) {
fg = filtergraphs[j];
for (k = 0; k < fg->nb_outputs; k++) {
AVFilterInOut *out = fg->outputs[k]->out_tmp;
if (out && !strcmp(out->name, map->linklabel)) {
ofilter = fg->outputs[k];
goto loop_end;
}
}
}
loop_end:
if (!ofilter) {
av_log(NULL, AV_LOG_FATAL, "Output with label '%s' does not exist "
"in any defined filter graph, or was already used elsewhere.\n", map->linklabel);
exit_program(1);
}
init_output_filter(ofilter, o, oc);
} else {
int src_idx = input_files[map->file_index]->ist_index + map->stream_index;
ist = input_streams[input_files[map->file_index]->ist_index + map->stream_index];
if (ist->user_set_discard == AVDISCARD_ALL) {
av_log(NULL, AV_LOG_FATAL, "Stream #%d:%d is disabled and cannot be mapped.\n",
map->file_index, map->stream_index);
exit_program(1);
}
if(o->subtitle_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE)
continue;
if(o-> audio_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO)
continue;
if(o-> video_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
continue;
if(o-> data_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_DATA)
continue;
ost = NULL;
switch (ist->st->codecpar->codec_type) {
case AVMEDIA_TYPE_VIDEO: ost = new_video_stream (o, oc, src_idx); break;
case AVMEDIA_TYPE_AUDIO: ost = new_audio_stream (o, oc, src_idx); break;
case AVMEDIA_TYPE_SUBTITLE: ost = new_subtitle_stream (o, oc, src_idx); break;
case AVMEDIA_TYPE_DATA: ost = new_data_stream (o, oc, src_idx); break;
case AVMEDIA_TYPE_ATTACHMENT: ost = new_attachment_stream(o, oc, src_idx); break;
case AVMEDIA_TYPE_UNKNOWN:
if (copy_unknown_streams) {
ost = new_unknown_stream (o, oc, src_idx);
break;
}
default:
av_log(NULL, ignore_unknown_streams ? AV_LOG_WARNING : AV_LOG_FATAL,
"Cannot map stream #%d:%d - unsupported type.\n",
map->file_index, map->stream_index);
if (!ignore_unknown_streams) {
av_log(NULL, AV_LOG_FATAL,
"If you want unsupported types ignored instead "
"of failing, please use the -ignore_unknown option\n"
"If you want them copied, please use -copy_unknown\n");
exit_program(1);
}
}
if (ost)
ost->sync_ist = input_streams[ input_files[map->sync_file_index]->ist_index
+ map->sync_stream_index];
}
}
}
/* handle attached files */
//处理附加文件，附加文件是什么？
for (i = 0; i < o->nb_attachments; i++) {
AVIOContext *pb;
uint8_t *attachment;
const char *p;
int64_t len;
if ((err = avio_open2(&pb, o->attachments[i], AVIO_FLAG_READ, &int_cb, NULL)) < 0) {
av_log(NULL, AV_LOG_FATAL, "Could not open attachment file %s.\n",
o->attachments[i]);
exit_program(1);
}
if ((len = avio_size(pb)) <= 0) {
av_log(NULL, AV_LOG_FATAL, "Could not get size of the attachment %s.\n",
o->attachments[i]);
exit_program(1);
}
if (len > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE ||
!(attachment = av_malloc(len + AV_INPUT_BUFFER_PADDING_SIZE))) {
av_log(NULL, AV_LOG_FATAL, "Attachment %s too large.\n",
o->attachments[i]);
exit_program(1);
}
avio_read(pb, attachment, len);
memset(attachment + len, 0, AV_INPUT_BUFFER_PADDING_SIZE);
//这里的附加数据就是h264中的sps，pps信息，填充在附加信息里
ost = new_attachment_stream(o, oc, -1);
ost->stream_copy = 0;
ost->attachment_filename = o->attachments[i];
ost->st->codecpar->extradata = attachment;
ost->st->codecpar->extradata_size = len;
p = strrchr(o->attachments[i], '/');
av_dict_set(&ost->st->metadata, "filename", (p && *p) ? p + 1 : o->attachments[i], AV_DICT_DONT_OVERWRITE);
avio_closep(&pb);
}
if (!oc->nb_streams && !(oc->oformat->flags & AVFMT_NOSTREAMS)) {
av_dump_format(oc, nb_output_files - 1, oc->url, 1);
av_log(NULL, AV_LOG_ERROR, "Output file #%d does not contain any stream\n", nb_output_files - 1);
exit_program(1);
}
/* check if all codec options have been used */
//检查未使用的参数选项
unused_opts = strip_specifiers(o->g->codec_opts);
for (i = of->ost_index; i < nb_output_streams; i++) {
e = NULL;
while ((e = av_dict_get(output_streams[i]->encoder_opts, "", e,
AV_DICT_IGNORE_SUFFIX)))
av_dict_set(&unused_opts, e->key, NULL, 0);
}
e = NULL;
//将未使用的参数选项进行打印信息提示
while ((e = av_dict_get(unused_opts, "", e, AV_DICT_IGNORE_SUFFIX))) {
const AVClass *class = avcodec_get_class();
const AVOption *option = av_opt_find(&class, e->key, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ);
const AVClass *fclass = avformat_get_class();
const AVOption *foption = av_opt_find(&fclass, e->key, NULL, 0,
AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ);
if (!option || foption)
continue;
if (!(option->flags & AV_OPT_FLAG_ENCODING_PARAM)) {
av_log(NULL, AV_LOG_ERROR, "Codec AVOption %s (%s) specified for "
"output file #%d (%s) is not an encoding option.\n", e->key,
option->help ? option->help : "", nb_output_files - 1,
filename);
exit_program(1);
}
// gop_timecode is injected by generic code but not always used
if (!strcmp(e->key, "gop_timecode"))
continue;
av_log(NULL, AV_LOG_WARNING, "Codec AVOption %s (%s) specified for "
"output file #%d (%s) has not been used for any stream. The most "
"likely reason is either wrong type (e.g. a video option with "
"no video streams) or that it is a private option of some encoder "
"which was not actually used for any stream.\n", e->key,
option->help ? option->help : "", nb_output_files - 1, filename);
}
av_dict_free(&unused_opts);
/* set the decoding_needed flags and create simple filtergraphs */
//设置解码需要的参数标志，并创建简单过滤器组
for (i = of->ost_index; i < nb_output_streams; i++) {
OutputStream *ost = output_streams[i];
if (ost->encoding_needed && ost->source_index >= 0) {
InputStream *ist = input_streams[ost->source_index];
ist->decoding_needed |= DECODING_FOR_OST;
if (ost->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO ||
ost->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
err = init_simple_filtergraph(ist, ost);
if (err < 0) {
av_log(NULL, AV_LOG_ERROR,
"Error initializing a simple filtergraph between streams "
"%d:%d->%d:%d\n", ist->file_index, ost->source_index,
nb_output_files - 1, ost->st->index);
exit_program(1);
}
}
}
/* set the filter output constraints */
//设置输出过滤去的约束条件
//给对应的流formats结构申请合适的内存
if (ost->filter) {
OutputFilter *f = ost->filter;
int count;
switch (ost->enc_ctx->codec_type) {
case AVMEDIA_TYPE_VIDEO:
f->frame_rate = ost->frame_rate;
f->width = ost->enc_ctx->width;
f->height = ost->enc_ctx->height;
if (ost->enc_ctx->pix_fmt != AV_PIX_FMT_NONE) {
f->format = ost->enc_ctx->pix_fmt;
} else if (ost->enc->pix_fmts) {
count = 0;
while (ost->enc->pix_fmts[count] != AV_PIX_FMT_NONE)
count++;
f->formats = av_mallocz_array(count + 1, sizeof(*f->formats));
if (!f->formats)
exit_program(1);
memcpy(f->formats, ost->enc->pix_fmts, (count + 1) * sizeof(*f->formats));
}
break;
case AVMEDIA_TYPE_AUDIO:
if (ost->enc_ctx->sample_fmt != AV_SAMPLE_FMT_NONE) {
f->format = ost->enc_ctx->sample_fmt;
} else if (ost->enc->sample_fmts) {
count = 0;
while (ost->enc->sample_fmts[count] != AV_SAMPLE_FMT_NONE)
count++;
f->formats = av_mallocz_array(count + 1, sizeof(*f->formats));
if (!f->formats)
exit_program(1);
memcpy(f->formats, ost->enc->sample_fmts, (count + 1) * sizeof(*f->formats));
}
if (ost->enc_ctx->sample_rate) {
f->sample_rate = ost->enc_ctx->sample_rate;
} else if (ost->enc->supported_samplerates) {
count = 0;
while (ost->enc->supported_samplerates[count])
count++;
f->sample_rates = av_mallocz_array(count + 1, sizeof(*f->sample_rates));
if (!f->sample_rates)
exit_program(1);
memcpy(f->sample_rates, ost->enc->supported_samplerates,
(count + 1) * sizeof(*f->sample_rates));
}
if (ost->enc_ctx->channels) {
f->channel_layout = av_get_default_channel_layout(ost->enc_ctx->channels);
} else if (ost->enc->channel_layouts) {
count = 0;
while (ost->enc->channel_layouts[count])
count++;
f->channel_layouts = av_mallocz_array(count + 1, sizeof(*f->channel_layouts));
if (!f->channel_layouts)
exit_program(1);
memcpy(f->channel_layouts, ost->enc->channel_layouts,
(count + 1) * sizeof(*f->channel_layouts));
}
break;
}
}
}
/* check filename in case of an image number is expected */
if (oc->oformat->flags & AVFMT_NEEDNUMBER) {
if (!av_filename_number_test(oc->url)) {
print_error(oc->url, AVERROR(EINVAL));
exit_program(1);
}
}
if (!(oc->oformat->flags & AVFMT_NOSTREAMS) && !input_stream_potentially_available) {
av_log(NULL, AV_LOG_ERROR,
"No input streams but output needs an input stream\n");
exit_program(1);
}
if (!(oc->oformat->flags & AVFMT_NOFILE)) {
/* test if it already exists to avoid losing precious files */
assert_file_overwrite(filename);
/* open the file */
if ((err = avio_open2(&oc->pb, filename, AVIO_FLAG_WRITE,
&oc->interrupt_callback,
&of->opts)) < 0) {
print_error(filename, err);
exit_program(1);
}
} else if (strcmp(oc->oformat->name, "image2")==0 && !av_filename_number_test(filename))
assert_file_overwrite(filename);
if (o->mux_preload) {
av_dict_set_int(&of->opts, "preload", o->mux_preload*AV_TIME_BASE, 0);
}
oc->max_delay = (int)(o->mux_max_delay * AV_TIME_BASE);
/* copy metadata */
for (i = 0; i < o->nb_metadata_map; i++) {
char *p;
int in_file_index = strtol(o->metadata_map[i].u.str, &p, 0);
if (in_file_index >= nb_input_files) {
av_log(NULL, AV_LOG_FATAL, "Invalid input file index %d while processing metadata maps\n", in_file_index);
exit_program(1);
}
copy_metadata(o->metadata_map[i].specifier, *p ? p + 1 : p, oc,
in_file_index >= 0 ?
input_files[in_file_index]->ctx : NULL, o);
}
/* copy chapters */
if (o->chapters_input_file >= nb_input_files) {
if (o->chapters_input_file == INT_MAX) {
/* copy chapters from the first input file that has them*/
o->chapters_input_file = -1;
for (i = 0; i < nb_input_files; i++)
if (input_files[i]->ctx->nb_chapters) {
o->chapters_input_file = i;
break;
}
} else {
av_log(NULL, AV_LOG_FATAL, "Invalid input file index %d in chapter mapping.\n",
o->chapters_input_file);
exit_program(1);
}
}
if (o->chapters_input_file >= 0)
copy_chapters(input_files[o->chapters_input_file], of,
!o->metadata_chapters_manual);
/* copy global metadata by default */
if (!o->metadata_global_manual && nb_input_files){
av_dict_copy(&oc->metadata, input_files[0]->ctx->metadata,
AV_DICT_DONT_OVERWRITE);
if(o->recording_time != INT64_MAX)
av_dict_set(&oc->metadata, "duration", NULL, 0);
av_dict_set(&oc->metadata, "creation_time", NULL, 0);
av_dict_set(&oc->metadata, "company_name", NULL, 0);
av_dict_set(&oc->metadata, "product_name", NULL, 0);
av_dict_set(&oc->metadata, "product_version", NULL, 0);
}
if (!o->metadata_streams_manual)
for (i = of->ost_index; i < nb_output_streams; i++) {
InputStream *ist;
if (output_streams[i]->source_index < 0) /* this is true e.g. for attached files */
continue;
ist = input_streams[output_streams[i]->source_index];
av_dict_copy(&output_streams[i]->st->metadata, ist->st->metadata, AV_DICT_DONT_OVERWRITE);
if (!output_streams[i]->stream_copy) {
av_dict_set(&output_streams[i]->st->metadata, "encoder", NULL, 0);
}
}
//接下来的内容被注释是手动设置，这里没明白手动设置什么内容，什么意思？
//初步理解是下指令行进行设置的内容，ts流会涉及到
/* process manually set programs */
for (i = 0; i < o->nb_program; i++) {
const char *p = o->program[i].u.str;
int progid = i+1;
AVProgram *program;
while(*p) {
const char *p2 = av_get_token(&p, ":");
const char *to_dealloc = p2;
char *key;
if (!p2)
break;
if(*p) p++;
key = av_get_token(&p2, "=");
if (!key || !*p2) {
av_freep(&to_dealloc);
av_freep(&key);
break;
}
p2++;
if (!strcmp(key, "program_num"))
progid = strtol(p2, NULL, 0);
av_freep(&to_dealloc);
av_freep(&key);
}
program = av_new_program(oc, progid);
p = o->program[i].u.str;
while(*p) {
const char *p2 = av_get_token(&p, ":");
const char *to_dealloc = p2;
char *key;
if (!p2)
break;
if(*p) p++;
key = av_get_token(&p2, "=");
if (!key) {
av_log(NULL, AV_LOG_FATAL,
"No '=' character in program string %s.\n",
p2);
exit_program(1);
}
if (!*p2)
exit_program(1);
p2++;
if (!strcmp(key, "title")) {
av_dict_set(&program->metadata, "title", p2, 0);
} else if (!strcmp(key, "program_num")) {
} else if (!strcmp(key, "st")) {
int st_num = strtol(p2, NULL, 0);
av_program_add_stream_index(oc, progid, st_num);
} else {
av_log(NULL, AV_LOG_FATAL, "Unknown program key %s.\n", key);
exit_program(1);
}
av_freep(&to_dealloc);
av_freep(&key);
}
}
/* process manually set metadata */
for (i = 0; i < o->nb_metadata; i++) {
AVDictionary **m;
char type, *val;
const char *stream_spec;
int index = 0, j, ret = 0;
val = strchr(o->metadata[i].u.str, '=');
if (!val) {
av_log(NULL, AV_LOG_FATAL, "No '=' character in metadata string %s.\n",
o->metadata[i].u.str);
exit_program(1);
}
*val++ = 0;
parse_meta_type(o->metadata[i].specifier, &type, &index, &stream_spec);
if (type == 's') {
for (j = 0; j < oc->nb_streams; j++) {
ost = output_streams[nb_output_streams - oc->nb_streams + j];
if ((ret = check_stream_specifier(oc, oc->streams[j], stream_spec)) > 0) {
if (!strcmp(o->metadata[i].u.str, "rotate")) {
char *tail;
double theta = av_strtod(val, &tail);
if (!*tail) {
ost->rotate_overridden = 1;
ost->rotate_override_value = theta;
}
} else {
av_dict_set(&oc->streams[j]->metadata, o->metadata[i].u.str, *val ? val : NULL, 0);
}
} else if (ret < 0)
exit_program(1);
}
}
else {
switch (type) {
case 'g':
m = &oc->metadata;
break;
case 'c':
if (index < 0 || index >= oc->nb_chapters) {
av_log(NULL, AV_LOG_FATAL, "Invalid chapter index %d in metadata specifier.\n", index);
exit_program(1);
}
m = &oc->chapters[index]->metadata;
break;
case 'p':
if (index < 0 || index >= oc->nb_programs) {
av_log(NULL, AV_LOG_FATAL, "Invalid program index %d in metadata specifier.\n", index);
exit_program(1);
}
m = &oc->programs[index]->metadata;
break;
default:
av_log(NULL, AV_LOG_FATAL, "Invalid metadata specifier %s.\n", o->metadata[i].specifier);
exit_program(1);
}
av_dict_set(m, o->metadata[i].u.str, *val ? val : NULL, 0);
}
}
return 0;
}
总结
ffmpeg_parse_options 函数总得对输入输出文件的上下文结构进行了填充，分类，转换为内部结构，方便下面的步骤使用。
参考
AVDictionary 介绍
sws和swr
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