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ffmpeg_opt.c
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ffmpeg_opt.c
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/*
* ffmpeg option parsing
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <stdint.h>
#include "ffmpeg.h"
#include "cmdutils.h"
#include "libavformat/avformat.h"
#include "libavcodec/avcodec.h"
#include "libavfilter/avfilter.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/avutil.h"
#include "libavutil/channel_layout.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/fifo.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"
#include "libavutil/parseutils.h"
#include "libavutil/pixdesc.h"
#include "libavutil/pixfmt.h"
#define DEFAULT_PASS_LOGFILENAME_PREFIX "ffmpeg2pass"
/**
* @brief 这里看到，MATCH_PER_STREAM_OPT的作用是，遍历用户所有的编解码器名字所属的音视频类型是否都与该流st的st->codecpar->codec_type一样，
* 如果存在一个不一样，那么程序直接退出；否则符合，当用户输入多个编解码器名字时，只会取最后一个编解码器名字作为返回.
* 例如用户传入：-vcodec libx265 -vcodec libx264，此时假设st是视频流，虽然h265,h264都是属于视频流类型的编解码器，但是只会返回用户最后一个
* 编解码器名字，即outvar="libx264"作为传出参数
*/
#define MATCH_PER_STREAM_OPT(name, type, outvar, fmtctx, st)\
{\
int i, ret;\
for (i = 0; i < o->nb_ ## name; i++) {\
char *spec = o->name[i].specifier;\
if ((ret = check_stream_specifier(fmtctx, st, spec)) > 0)\
outvar = o->name[i].u.type;\
else if (ret < 0)\
exit_program(1);\
}\
}
#define MATCH_PER_TYPE_OPT(name, type, outvar, fmtctx, mediatype)\
{\
int i;\
for (i = 0; i < o->nb_ ## name; i++) {\
char *spec = o->name[i].specifier;\
if (!strcmp(spec, mediatype))\
outvar = o->name[i].u.type;\
}\
}
const HWAccel hwaccels[] = {
#if CONFIG_VIDEOTOOLBOX
{ "videotoolbox", videotoolbox_init, HWACCEL_VIDEOTOOLBOX, AV_PIX_FMT_VIDEOTOOLBOX },
#endif
#if CONFIG_LIBMFX
{ "qsv", qsv_init, HWACCEL_QSV, AV_PIX_FMT_QSV },
#endif
#if CONFIG_CUVID
{ "cuvid", cuvid_init, HWACCEL_CUVID, AV_PIX_FMT_CUDA },
#endif
{ 0 },
};
AVBufferRef *hw_device_ctx;
HWDevice *filter_hw_device;
char *vstats_filename;
char *sdp_filename;
float audio_drift_threshold = 0.1;
float dts_delta_threshold = 10;
float dts_error_threshold = 3600*30; // dts错误阈值,默认30小时.帧能被解码的最大阈值大小？
int audio_volume = 256; // -vol选项,默认256
int audio_sync_method = 0; // 音频同步方法.默认0
int video_sync_method = VSYNC_AUTO;
float frame_drop_threshold = 0;
int do_deinterlace = 0; // -deinterlace选项,默认0.
int do_benchmark = 0;
int do_benchmark_all = 0; // -benchmark_all选项，默认0
int do_hex_dump = 0;
int do_pkt_dump = 0;
int copy_ts = 0; // copy timestamps,默认0
int start_at_zero = 0; // 使用copy_ts时，将输入时间戳移至0开始,默认0
int copy_tb = -1;
int debug_ts = 0; // 是否打印相关时间戳.-debug_ts选项
int exit_on_error = 0; // xerror选项,默认是0
int abort_on_flags = 0;
int print_stats = -1; // -stats选项,默认-1,在编码期间打印进度报告.
int qp_hist = 0; // -qphist选项,默认0,显示QP直方图
int stdin_interaction = 1; // 可认为是否是交互模式.除pipe、以及/dev/stdin值为0，其它例如普通文件、实时流都是1
int frame_bits_per_raw_sample = 0;
float max_error_rate = 2.0/3;
int filter_nbthreads = 0; // -filter_threads选项,默认0,非复杂过滤器线程数.
int filter_complex_nbthreads = 0; // -filter_complex_threads选项,默认0,复杂过滤器线程数.
int vstats_version = 2; // -vstats_version选项, 默认2, 要使用的vstats格式的版本
static int intra_only = 0;
static int file_overwrite = 0; // -y选项，重写输出文件，即覆盖该输出文件。0=不重写，1=重写，
// 不过为0时且no_file_overwrite=0时会在终端询问用户是否重写
static int no_file_overwrite = 0; // -n选项，不重写输出文件。0=不重写，1=重写
static int do_psnr = 0;
static int input_sync;
static int input_stream_potentially_available = 0;// 标记，=1代表该输入文件可能是可用的
static int ignore_unknown_streams = 0;
static int copy_unknown_streams = 0;
static int find_stream_info = 1;
void tyy_print_AVDirnary(AVDictionary *d){
if(!d){
return;
}
AVDictionaryEntry *t = NULL;
while((t = av_dict_get(d, "", t, AV_DICT_IGNORE_SUFFIX))){
printf("tyy_print_AVDirnary, t->key: %s, t->value: %s\n", t->key, t->value);
}
}
static void uninit_options(OptionsContext *o)
{
const OptionDef *po = options;
int i;
/* all OPT_SPEC and OPT_STRING can be freed in generic way */
while (po->name) {
void *dst = (uint8_t*)o + po->u.off;
// 1. 保存在SpecifierOpt结构的，需要被释放
if (po->flags & OPT_SPEC) {
SpecifierOpt **so = dst;
int i, *count = (int*)(so + 1);
for (i = 0; i < *count; i++) {
av_freep(&(*so)[i].specifier);
if (po->flags & OPT_STRING)
av_freep(&(*so)[i].u.str);
}
av_freep(so);
*count = 0;
} else if (po->flags & OPT_OFFSET && po->flags & OPT_STRING)
// 2. 具有OPT_OFFSET标志且是字符串，同样需要被释放
av_freep(dst);
po++;
}
for (i = 0; i < o->nb_stream_maps; i++)
av_freep(&o->stream_maps[i].linklabel);
av_freep(&o->stream_maps);
av_freep(&o->audio_channel_maps);
av_freep(&o->streamid_map);
av_freep(&o->attachments);
}
static void init_options(OptionsContext *o)
{
memset(o, 0, sizeof(*o));
o->stop_time = INT64_MAX;
o->mux_max_delay = 0.7;
o->start_time = AV_NOPTS_VALUE;
o->start_time_eof = AV_NOPTS_VALUE;
o->recording_time = INT64_MAX;
o->limit_filesize = UINT64_MAX;
o->chapters_input_file = INT_MAX;
o->accurate_seek = 1;
}
static int show_hwaccels(void *optctx, const char *opt, const char *arg)
{
enum AVHWDeviceType type = AV_HWDEVICE_TYPE_NONE;
int i;
printf("Hardware acceleration methods:\n");
while ((type = av_hwdevice_iterate_types(type)) !=
AV_HWDEVICE_TYPE_NONE)
printf("%s\n", av_hwdevice_get_type_name(type));
for (i = 0; hwaccels[i].name; i++)
printf("%s\n", hwaccels[i].name);
printf("\n");
return 0;
}
/**
* @brief 将传进来的字典内的键值对，去掉流说明符后，设置到新的字典进行返回，传进来的字典内容保持不变。
* @param dict 原字典
* @return 返回一个新的没有流说明符的字典
*/
/* return a copy of the input with the stream specifiers removed from the keys-返回输入的副本，并从键中删除流说明符 */
static AVDictionary *strip_specifiers(AVDictionary *dict)
{
AVDictionaryEntry *e = NULL;
AVDictionary *ret = NULL;
while ((e = av_dict_get(dict, "", e, AV_DICT_IGNORE_SUFFIX))) {
char *p = strchr(e->key, ':');
/*将流说明符去掉.例如e->key="b:v"，p是指向":v"的，那么*p=0后，e->key="b"*/
if (p)
*p = 0;
/*所以这里设置到ret的，必定是去掉流说明符"v"的(冒号是分隔符当然也会去掉)，例如e->key="b"，e->value="128K"*/
av_dict_set(&ret, e->key, e->value, 0);
/*上面设置完毕后，将该p指向的地址恢复为分隔符":"，此时会恢复原来的值：e->key="b:v"*/
if (p)
*p = ':';
}
return ret;
}
// 中止指定的条件标志
static int opt_abort_on(void *optctx, const char *opt, const char *arg)
{
static const AVOption opts[] = {
{ "abort_on" , NULL, 0, AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT64_MIN, INT64_MAX, .unit = "flags" },
{ "empty_output" , NULL, 0, AV_OPT_TYPE_CONST, { .i64 = ABORT_ON_FLAG_EMPTY_OUTPUT }, .unit = "flags" },
{ NULL },
};
static const AVClass class = {
.class_name = "",
.item_name = av_default_item_name,
.option = opts,
.version = LIBAVUTIL_VERSION_INT,
};
const AVClass *pclass = &class;
return av_opt_eval_flags(&pclass, &opts[0], arg, &abort_on_flags);// 使用参3给参4赋值.
}
static int opt_sameq(void *optctx, const char *opt, const char *arg)
{
av_log(NULL, AV_LOG_ERROR, "Option '%s' was removed. "
"If you are looking for an option to preserve the quality (which is not "
"what -%s was for), use -qscale 0 or an equivalent quality factor option.\n",
opt, opt);
return AVERROR(EINVAL);
}
static int opt_video_channel(void *optctx, const char *opt, const char *arg)
{
av_log(NULL, AV_LOG_WARNING, "This option is deprecated, use -channel.\n");
return opt_default(optctx, "channel", arg);
}
static int opt_video_standard(void *optctx, const char *opt, const char *arg)
{
av_log(NULL, AV_LOG_WARNING, "This option is deprecated, use -standard.\n");
return opt_default(optctx, "standard", arg);
}
static int opt_audio_codec(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
return parse_option(o, "codec:a", arg, options);
}
static int opt_video_codec(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
return parse_option(o, "codec:v", arg, options);
}
static int opt_subtitle_codec(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
return parse_option(o, "codec:s", arg, options);
}
static int opt_data_codec(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
return parse_option(o, "codec:d", arg, options);
}
static int opt_map(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
StreamMap *m = NULL;
int i, negative = 0, file_idx, disabled = 0;
int sync_file_idx = -1, sync_stream_idx = 0;
char *p, *sync;
char *map;
char *allow_unused;
if (*arg == '-') {
negative = 1;
arg++;
}
map = av_strdup(arg);
if (!map)
return AVERROR(ENOMEM);
/* parse sync stream first, just pick first matching stream */
if (sync = strchr(map, ',')) {
*sync = 0;
sync_file_idx = strtol(sync + 1, &sync, 0);
if (sync_file_idx >= nb_input_files || sync_file_idx < 0) {
av_log(NULL, AV_LOG_FATAL, "Invalid sync file index: %d.\n", sync_file_idx);
exit_program(1);
}
if (*sync)
sync++;
for (i = 0; i < input_files[sync_file_idx]->nb_streams; i++)
if (check_stream_specifier(input_files[sync_file_idx]->ctx,
input_files[sync_file_idx]->ctx->streams[i], sync) == 1) {
sync_stream_idx = i;
break;
}
if (i == input_files[sync_file_idx]->nb_streams) {
av_log(NULL, AV_LOG_FATAL, "Sync stream specification in map %s does not "
"match any streams.\n", arg);
exit_program(1);
}
if (input_streams[input_files[sync_file_idx]->ist_index + sync_stream_idx]->user_set_discard == AVDISCARD_ALL) {
av_log(NULL, AV_LOG_FATAL, "Sync stream specification in map %s matches a disabled input "
"stream.\n", arg);
exit_program(1);
}
}
if (map[0] == '[') {
/* this mapping refers to lavfi output */
const char *c = map + 1;
GROW_ARRAY(o->stream_maps, o->nb_stream_maps);
m = &o->stream_maps[o->nb_stream_maps - 1];
m->linklabel = av_get_token(&c, "]");
if (!m->linklabel) {
av_log(NULL, AV_LOG_ERROR, "Invalid output link label: %s.\n", map);
exit_program(1);
}
} else {
if (allow_unused = strchr(map, '?'))
*allow_unused = 0;
file_idx = strtol(map, &p, 0);
if (file_idx >= nb_input_files || file_idx < 0) {
av_log(NULL, AV_LOG_FATAL, "Invalid input file index: %d.\n", file_idx);
exit_program(1);
}
if (negative)
/* disable some already defined maps */
for (i = 0; i < o->nb_stream_maps; i++) {
m = &o->stream_maps[i];
if (file_idx == m->file_index &&
check_stream_specifier(input_files[m->file_index]->ctx,
input_files[m->file_index]->ctx->streams[m->stream_index],
*p == ':' ? p + 1 : p) > 0)
m->disabled = 1;
}
else
for (i = 0; i < input_files[file_idx]->nb_streams; i++) {
if (check_stream_specifier(input_files[file_idx]->ctx, input_files[file_idx]->ctx->streams[i],
*p == ':' ? p + 1 : p) <= 0)
continue;
if (input_streams[input_files[file_idx]->ist_index + i]->user_set_discard == AVDISCARD_ALL) {
disabled = 1;
continue;
}
GROW_ARRAY(o->stream_maps, o->nb_stream_maps);
m = &o->stream_maps[o->nb_stream_maps - 1];
m->file_index = file_idx;
m->stream_index = i;
if (sync_file_idx >= 0) {
m->sync_file_index = sync_file_idx;
m->sync_stream_index = sync_stream_idx;
} else {
m->sync_file_index = file_idx;
m->sync_stream_index = i;
}
}
}
if (!m) {
if (allow_unused) {
av_log(NULL, AV_LOG_VERBOSE, "Stream map '%s' matches no streams; ignoring.\n", arg);
} else if (disabled) {
av_log(NULL, AV_LOG_FATAL, "Stream map '%s' matches disabled streams.\n"
"To ignore this, add a trailing '?' to the map.\n", arg);
exit_program(1);
} else {
av_log(NULL, AV_LOG_FATAL, "Stream map '%s' matches no streams.\n"
"To ignore this, add a trailing '?' to the map.\n", arg);
exit_program(1);
}
}
av_freep(&map);
return 0;
}
static int opt_attach(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
GROW_ARRAY(o->attachments, o->nb_attachments);
o->attachments[o->nb_attachments - 1] = arg;
return 0;
}
static int opt_map_channel(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
int n;
AVStream *st;
AudioChannelMap *m;
char *allow_unused;
char *mapchan;
mapchan = av_strdup(arg);
if (!mapchan)
return AVERROR(ENOMEM);
GROW_ARRAY(o->audio_channel_maps, o->nb_audio_channel_maps);
m = &o->audio_channel_maps[o->nb_audio_channel_maps - 1];
/* muted channel syntax */
n = sscanf(arg, "%d:%d.%d", &m->channel_idx, &m->ofile_idx, &m->ostream_idx);
if ((n == 1 || n == 3) && m->channel_idx == -1) {
m->file_idx = m->stream_idx = -1;
if (n == 1)
m->ofile_idx = m->ostream_idx = -1;
av_free(mapchan);
return 0;
}
/* normal syntax */
n = sscanf(arg, "%d.%d.%d:%d.%d",
&m->file_idx, &m->stream_idx, &m->channel_idx,
&m->ofile_idx, &m->ostream_idx);
if (n != 3 && n != 5) {
av_log(NULL, AV_LOG_FATAL, "Syntax error, mapchan usage: "
"[file.stream.channel|-1][:syncfile:syncstream]\n");
exit_program(1);
}
if (n != 5) // only file.stream.channel specified
m->ofile_idx = m->ostream_idx = -1;
/* check input */
if (m->file_idx < 0 || m->file_idx >= nb_input_files) {
av_log(NULL, AV_LOG_FATAL, "mapchan: invalid input file index: %d\n",
m->file_idx);
exit_program(1);
}
if (m->stream_idx < 0 ||
m->stream_idx >= input_files[m->file_idx]->nb_streams) {
av_log(NULL, AV_LOG_FATAL, "mapchan: invalid input file stream index #%d.%d\n",
m->file_idx, m->stream_idx);
exit_program(1);
}
st = input_files[m->file_idx]->ctx->streams[m->stream_idx];
if (st->codecpar->codec_type != AVMEDIA_TYPE_AUDIO) {
av_log(NULL, AV_LOG_FATAL, "mapchan: stream #%d.%d is not an audio stream.\n",
m->file_idx, m->stream_idx);
exit_program(1);
}
/* allow trailing ? to map_channel */
if (allow_unused = strchr(mapchan, '?'))
*allow_unused = 0;
if (m->channel_idx < 0 || m->channel_idx >= st->codecpar->channels ||
input_streams[input_files[m->file_idx]->ist_index + m->stream_idx]->user_set_discard == AVDISCARD_ALL) {
if (allow_unused) {
av_log(NULL, AV_LOG_VERBOSE, "mapchan: invalid audio channel #%d.%d.%d\n",
m->file_idx, m->stream_idx, m->channel_idx);
} else {
av_log(NULL, AV_LOG_FATAL, "mapchan: invalid audio channel #%d.%d.%d\n"
"To ignore this, add a trailing '?' to the map_channel.\n",
m->file_idx, m->stream_idx, m->channel_idx);
exit_program(1);
}
}
av_free(mapchan);
return 0;
}
static int opt_sdp_file(void *optctx, const char *opt, const char *arg)
{
av_free(sdp_filename);
sdp_filename = av_strdup(arg);
return 0;
}
#if CONFIG_VAAPI
static int opt_vaapi_device(void *optctx, const char *opt, const char *arg)
{
HWDevice *dev;
const char *prefix = "vaapi:";
char *tmp;
int err;
tmp = av_asprintf("%s%s", prefix, arg);
if (!tmp)
return AVERROR(ENOMEM);
err = hw_device_init_from_string(tmp, &dev);
av_free(tmp);
if (err < 0)
return err;
hw_device_ctx = av_buffer_ref(dev->device_ref);
if (!hw_device_ctx)
return AVERROR(ENOMEM);
return 0;
}
#endif
// -init_hw_device选项的回调
static int opt_init_hw_device(void *optctx, const char *opt, const char *arg)
{
if (!strcmp(arg, "list")) {
enum AVHWDeviceType type = AV_HWDEVICE_TYPE_NONE;
printf("Supported hardware device types:\n");
while ((type = av_hwdevice_iterate_types(type)) !=
AV_HWDEVICE_TYPE_NONE)
printf("%s\n", av_hwdevice_get_type_name(type));
printf("\n");
exit_program(0);
} else {
return hw_device_init_from_string(arg, NULL);
}
}
static int opt_filter_hw_device(void *optctx, const char *opt, const char *arg)
{
if (filter_hw_device) {
av_log(NULL, AV_LOG_ERROR, "Only one filter device can be used.\n");
return AVERROR(EINVAL);
}
filter_hw_device = hw_device_get_by_name(arg);
if (!filter_hw_device) {
av_log(NULL, AV_LOG_ERROR, "Invalid filter device %s.\n", arg);
return AVERROR(EINVAL);
}
return 0;
}
/**
* Parse a metadata specifier passed as 'arg' parameter.
* @param arg metadata string to parse
* @param type metadata type is written here -- g(lobal)/s(tream)/c(hapter)/p(rogram)
* @param index for type c/p, chapter/program index is written here
* @param stream_spec for type s, the stream specifier is written here
*/
static void parse_meta_type(char *arg, char *type, int *index, const char **stream_spec)
{
if (*arg) {
*type = *arg;
switch (*arg) {
case 'g':
break;
case 's':
if (*(++arg) && *arg != ':') {
av_log(NULL, AV_LOG_FATAL, "Invalid metadata specifier %s.\n", arg);
exit_program(1);
}
*stream_spec = *arg == ':' ? arg + 1 : "";
break;
case 'c':
case 'p':
if (*(++arg) == ':')
*index = strtol(++arg, NULL, 0);
break;
default:
av_log(NULL, AV_LOG_FATAL, "Invalid metadata type %c.\n", *arg);
exit_program(1);
}
} else
*type = 'g';
}
static int copy_metadata(char *outspec, char *inspec, AVFormatContext *oc, AVFormatContext *ic, OptionsContext *o)
{
AVDictionary **meta_in = NULL;
AVDictionary **meta_out = NULL;
int i, ret = 0;
char type_in, type_out;
const char *istream_spec = NULL, *ostream_spec = NULL;
int idx_in = 0, idx_out = 0;
parse_meta_type(inspec, &type_in, &idx_in, &istream_spec);
parse_meta_type(outspec, &type_out, &idx_out, &ostream_spec);
if (!ic) {
if (type_out == 'g' || !*outspec)
o->metadata_global_manual = 1;
if (type_out == 's' || !*outspec)
o->metadata_streams_manual = 1;
if (type_out == 'c' || !*outspec)
o->metadata_chapters_manual = 1;
return 0;
}
if (type_in == 'g' || type_out == 'g')
o->metadata_global_manual = 1;
if (type_in == 's' || type_out == 's')
o->metadata_streams_manual = 1;
if (type_in == 'c' || type_out == 'c')
o->metadata_chapters_manual = 1;
/* ic is NULL when just disabling automatic mappings */
if (!ic)
return 0;
#define METADATA_CHECK_INDEX(index, nb_elems, desc)\
if ((index) < 0 || (index) >= (nb_elems)) {\
av_log(NULL, AV_LOG_FATAL, "Invalid %s index %d while processing metadata maps.\n",\
(desc), (index));\
exit_program(1);\
}
#define SET_DICT(type, meta, context, index)\
switch (type) {\
case 'g':\
meta = &context->metadata;\
break;\
case 'c':\
METADATA_CHECK_INDEX(index, context->nb_chapters, "chapter")\
meta = &context->chapters[index]->metadata;\
break;\
case 'p':\
METADATA_CHECK_INDEX(index, context->nb_programs, "program")\
meta = &context->programs[index]->metadata;\
break;\
case 's':\
break; /* handled separately below */ \
default: av_assert0(0);\
}\
SET_DICT(type_in, meta_in, ic, idx_in);
SET_DICT(type_out, meta_out, oc, idx_out);
/* for input streams choose first matching stream */
if (type_in == 's') {
for (i = 0; i < ic->nb_streams; i++) {
if ((ret = check_stream_specifier(ic, ic->streams[i], istream_spec)) > 0) {
meta_in = &ic->streams[i]->metadata;
break;
} else if (ret < 0)
exit_program(1);
}
if (!meta_in) {
av_log(NULL, AV_LOG_FATAL, "Stream specifier %s does not match any streams.\n", istream_spec);
exit_program(1);
}
}
if (type_out == 's') {
for (i = 0; i < oc->nb_streams; i++) {
if ((ret = check_stream_specifier(oc, oc->streams[i], ostream_spec)) > 0) {
meta_out = &oc->streams[i]->metadata;
av_dict_copy(meta_out, *meta_in, AV_DICT_DONT_OVERWRITE);
} else if (ret < 0)
exit_program(1);
}
} else
av_dict_copy(meta_out, *meta_in, AV_DICT_DONT_OVERWRITE);
return 0;
}
static int opt_recording_timestamp(void *optctx, const char *opt, const char *arg)
{
OptionsContext *o = optctx;
char buf[128];
int64_t recording_timestamp = parse_time_or_die(opt, arg, 0) / 1E6;
struct tm time = *gmtime((time_t*)&recording_timestamp);
if (!strftime(buf, sizeof(buf), "creation_time=%Y-%m-%dT%H:%M:%S%z", &time))
return -1;
parse_option(o, "metadata", buf, options);
av_log(NULL, AV_LOG_WARNING, "%s is deprecated, set the 'creation_time' metadata "
"tag instead.\n", opt);
return 0;
}
/**
* @brief
* @param name 要寻找的编解码器名字
* @param type 媒体类型
* @param encoder 要进行编码还是解码.0 解码， 1 编码
* @return 成功 返回找到的编解码器; 失败 程序退出
*/
static AVCodec *find_codec_or_die(const char *name, enum AVMediaType type, int encoder)
{
const AVCodecDescriptor *desc;
const char *codec_string = encoder ? "encoder" : "decoder";
AVCodec *codec;
// 1. 根据名字寻找编解码器
codec = encoder ?
avcodec_find_encoder_by_name(name) :
avcodec_find_decoder_by_name(name);
// 2. 如果根据名字找不到，则使用名字先找编解码器的描述符，再使用描述符寻找编解码器.
if (!codec && (desc = avcodec_descriptor_get_by_name(name))) {// 根据名字获取编解码器的描述符
codec = encoder ? avcodec_find_encoder(desc->id) :
avcodec_find_decoder(desc->id);
if (codec)
av_log(NULL, AV_LOG_VERBOSE, "Matched %s '%s' for codec '%s'.\n",
codec_string, codec->name, desc->name);
}
if (!codec) {
av_log(NULL, AV_LOG_FATAL, "Unknown %s '%s'\n", codec_string, name);
exit_program(1);
}
// 3. 对比.根据用户传进的名字找到的编解码器的媒体类型，若与用户传进的不一致，退出程序.
// 例如用户传进:-codec:a libx264，那么MATCH_PER_TYPE_OPT匹配时，audio_codec_name="libx264"
// 虽然找到编解码器，但音频是没有libx264的，这个找到编解码器是视频的，所以退出.
// codec->type是通过用户输入的名字找到的编解码器名字的类型
if (codec->type != type) {
av_log(NULL, AV_LOG_FATAL, "Invalid %s type '%s'\n", codec_string, name);
exit_program(1);
}
return codec;
}
// 例如将choose_decoder的MATCH_PER_STREAM_OPT展开来，用于debug
/**
* @brief 这里看到，MATCH_PER_STREAM_OPT的作用是，遍历用户所有的编解码器名字所属的音视频类型是否都与该流st的st->codecpar->codec_type一样，
* 如果存在一个不一样，那么程序直接退出；否则当用户输入多个编解码器名字时，只会取最后一个编解码器名字作为返回.
* 例如用户传入：-vcodec libx265 -vcodec libx264，此时假设st是视频流，虽然h265,h264都是属于视频流类型的编解码器，但是只会返回用户最后一个
* 编解码器名字，即outvar="libx264"作为传出参数
*/
void MATCH_PER_STREAM_OPT_TYYCODE(OptionsContext *o,const char* name, const char *type,
char *outvar, AVFormatContext* fmtctx, AVStream *st){
int i, ret;
for (i = 0; i < o->nb_codec_names; i++) {
char *spec = o->codec_names[i].specifier;
if ((ret = check_stream_specifier(fmtctx, st, spec)) > 0)
outvar = o->codec_names[i].u.str;
else if (ret < 0)
exit_program(1);
}
}
/**
* @brief 选择解码器以及对应的解码器id.两种方案：
* 1.用户传进解码器，那么返回用户选择的解码器，并且st保存了用户选择的解码器的codec_id；
* 2.用户无传进解码器，则以流中的codec_id作为选择解码器返回, codec_id无需改变.
* 当用户传了 解码器选项时，若音视频类型与流的音视频类型不一致 或者 解码器不被ffmpeg支持，程序会退出.
*
* 实际上该函数不关心返回值的话，就是应用强制解码器id(apply forced codec ids)
*/
static AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVStream *st)
{
char *codec_name = NULL;
MATCH_PER_STREAM_OPT(codec_names, str, codec_name, s, st);// 判断音视频类型是否与流一致.例如-vcodec libx264,这里是判断'v'是否与st的codec_type一致
if (codec_name) {
AVCodec *codec = find_codec_or_die(codec_name, st->codecpar->codec_type, 0);// 判断解码器是否被ffmpeg支持.例如-vcodec libx264,这里是判断 libx264是否被ffmpeg支持
st->codecpar->codec_id = codec->id;
return codec;
} else
return avcodec_find_decoder(st->codecpar->codec_id);
}
/* Add all the streams from the given input file to the global
* list of input streams. */
// 该函数实际上是对输入流中解码器相关参数的处理，然后封装到InputStream结构体中
static void add_input_streams(OptionsContext *o, AVFormatContext *ic)
{
int i, ret;
for (i = 0; i < ic->nb_streams; i++) {
AVStream *st = ic->streams[i];
AVCodecParameters *par = st->codecpar;
InputStream *ist = av_mallocz(sizeof(*ist));
char *framerate = NULL, *hwaccel_device = NULL;
const char *hwaccel = NULL;
char *hwaccel_output_format = NULL;
char *codec_tag = NULL;
char *next;
char *discard_str = NULL;
const AVClass *cc = avcodec_get_class();// 获取AVCodecContext的AVClass
const AVOption *discard_opt = av_opt_find(&cc, "skip_frame", NULL, 0, 0);
if (!ist)
exit_program(1);
// 1. 往二维数组input_streams**增加一个input_streams*元素
GROW_ARRAY(input_streams, nb_input_streams);//注：这里只是开辟了InputStream *字节大小(64bit为8字节)，而不是开辟InputStream字节大小(sizeof(InputStream))
input_streams[nb_input_streams - 1] = ist;
// 2. 利用o对InputStream内部进行赋值或者直接赋默认值
ist->st = st;
ist->file_index = nb_input_files;
ist->discard = 1;
st->discard = AVDISCARD_ALL;/*设置了AVDISCARD_ALL，表示用户丢弃该流*/
ist->nb_samples = 0;
ist->min_pts = INT64_MAX;
ist->max_pts = INT64_MIN;
ist->ts_scale = 1.0;
MATCH_PER_STREAM_OPT(ts_scale, dbl, ist->ts_scale, ic, st);
ist->autorotate = 1;
MATCH_PER_STREAM_OPT(autorotate, i, ist->autorotate, ic, st);
MATCH_PER_STREAM_OPT(codec_tags, str, codec_tag, ic, st);
if (codec_tag) {
//strtlo see https://blog.csdn.net/weixin_37921201/article/details/119718403
uint32_t tag = strtol(codec_tag, &next, 0);// next指向非法字符串开始及后面的字符串.
if (*next)// codec_tag出现非法字符串的处理
tag = AV_RL32(codec_tag);
st->codecpar->codec_tag = tag;
}
// 3. 保存解码器
ist->dec = choose_decoder(o, ic, st);
// 4. 保存解码器选项。将o->g->codec_opts保存的解码器选项通过返回值设置到decoder_opts中。
/*这里看到，每个流都保存了一份o->g->codec_opts*/
ist->decoder_opts = filter_codec_opts(o->g->codec_opts, ist->st->codecpar->codec_id, ic, st, ist->dec);
ist->reinit_filters = -1;
MATCH_PER_STREAM_OPT(reinit_filters, i, ist->reinit_filters, ic, st);
MATCH_PER_STREAM_OPT(discard, str, discard_str, ic, st);
ist->user_set_discard = AVDISCARD_NONE;/*默认该流是不丢弃的*/
// 5. 判断是否丢弃该流.-vn,-an,-sn这些选项.
// 只要有视频或者音频或者字幕或者数据被禁用，那么user_set_discard标记为AVDISCARD_ALL
if ((o->video_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) ||
(o->audio_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) ||
(o->subtitle_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE) ||
(o->data_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_DATA))
ist->user_set_discard = AVDISCARD_ALL;/*设置了AVDISCARD_ALL，表示用户丢弃该流*/
/*检测ffmpeg设置后user_set_discard的值是否与用户的一致，不一致则程序退出*/
if (discard_str && av_opt_eval_int(&cc, discard_opt, discard_str, &ist->user_set_discard) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error parsing discard %s.\n",
discard_str);
exit_program(1);
}
ist->filter_in_rescale_delta_last = AV_NOPTS_VALUE;
// 6. 为解码器上下文开辟内存
ist->dec_ctx = avcodec_alloc_context3(ist->dec);
if (!ist->dec_ctx) {
av_log(NULL, AV_LOG_ERROR, "Error allocating the decoder context.\n");
exit_program(1);
}
// 7. 从流中拷贝参数到解码器上下文
ret = avcodec_parameters_to_context(ist->dec_ctx, par);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error initializing the decoder context.\n");
exit_program(1);
}
if (o->bitexact)
ist->dec_ctx->flags |= AV_CODEC_FLAG_BITEXACT;
// 8. 给不同媒体类型的InputStream中的编解码器相关成员赋值.(忽略硬件相关内容)
switch (par->codec_type) {
case AVMEDIA_TYPE_VIDEO:
if(!ist->dec)// 一般在choose_decoder时已经找到，注open_input_files找到的解码器是ic中的，这里是ist
ist->dec = avcodec_find_decoder(par->codec_id);
#if FF_API_LOWRES
if (st->codec->lowres) {
ist->dec_ctx->lowres = st->codec->lowres;
ist->dec_ctx->width = st->codec->width;
ist->dec_ctx->height = st->codec->height;
ist->dec_ctx->coded_width = st->codec->coded_width;
ist->dec_ctx->coded_height = st->codec->coded_height;
}
#endif
// avformat_find_stream_info() doesn't set this for us anymore.
// avformat_find_stream_info()不再为我们设置这个。
ist->dec_ctx->framerate = st->avg_frame_rate;
MATCH_PER_STREAM_OPT(frame_rates, str, framerate, ic, st);
if (framerate && av_parse_video_rate(&ist->framerate,
framerate) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error parsing framerate %s.\n",
framerate);
exit_program(1);
}
ist->top_field_first = -1;
MATCH_PER_STREAM_OPT(top_field_first, i, ist->top_field_first, ic, st);
// 硬件加速相关.
// 寻找硬件设备的id
MATCH_PER_STREAM_OPT(hwaccels, str, hwaccel, ic, st);
if (hwaccel) {
// The NVDEC hwaccels use a CUDA device, so remap the name here.
// NVDEC hwaccels使用CUDA设备，所以在这里重新映射名称。
// NVDEC是英伟达提供的一种视频解码器引擎，作用是用来解码，可认为是一个SDK库。see https://blog.csdn.net/qq_18998145/article/details/108535188
// cuda则是一种架构，使用CPU+GPU去处理各种复杂的运算。see https://baike.baidu.com/item/CUDA/1186262?fr=aladdin
// 所以这里再重新看这段代码：因为nvdec内部使用的是cuda架构，所以重新映射hwaccel字符串
if (!strcmp(hwaccel, "nvdec"))
hwaccel = "cuda";
if (!strcmp(hwaccel, "none"))
ist->hwaccel_id = HWACCEL_NONE;
else if (!strcmp(hwaccel, "auto"))
ist->hwaccel_id = HWACCEL_AUTO;
else {// 用户指定了具体的硬件解码器
enum AVHWDeviceType type;
int i;
for (i = 0; hwaccels[i].name; i++) {
if (!strcmp(hwaccels[i].name, hwaccel)) {
ist->hwaccel_id = hwaccels[i].id;
break;
}
}
// hwaccel_id=HWACCEL_NONE时
if (!ist->hwaccel_id) {
// 根据设备类型名称查找，该函数不区分大小写。找不到会返回AV_HWDEVICE_TYPE_NONE
type = av_hwdevice_find_type_by_name(hwaccel);
if (type != AV_HWDEVICE_TYPE_NONE) {
ist->hwaccel_id = HWACCEL_GENERIC;
ist->hwaccel_device_type = type;
}
}
// hwaccel_id还是为HWACCEL_NONE时，打印相关错误提示然后程序退出
if (!ist->hwaccel_id) {
av_log(NULL, AV_LOG_FATAL, "Unrecognized hwaccel: %s.\n",
hwaccel);
av_log(NULL, AV_LOG_FATAL, "Supported hwaccels: ");
type = AV_HWDEVICE_TYPE_NONE;
// av_hwdevice_iterate_types函数每次会返回在hw_table中，上一个id为prev的硬件解码器id
// hw_table是源码中的一个硬件映射表，保存了各个解码器的处理函数
while ((type = av_hwdevice_iterate_types(type)) !=
AV_HWDEVICE_TYPE_NONE)
av_log(NULL, AV_LOG_FATAL, "%s ",
av_hwdevice_get_type_name(type));
for (i = 0; hwaccels[i].name; i++)
av_log(NULL, AV_LOG_FATAL, "%s ", hwaccels[i].name);
av_log(NULL, AV_LOG_FATAL, "\n");
exit_program(1);
}
}
}//<== if (hwaccel) end ==>
// 从命令行的参数获取硬件设备名
MATCH_PER_STREAM_OPT(hwaccel_devices, str, hwaccel_device, ic, st);
if (hwaccel_device) {
ist->hwaccel_device = av_strdup(hwaccel_device);
if (!ist->hwaccel_device)
exit_program(1);
}
MATCH_PER_STREAM_OPT(hwaccel_output_formats, str,
hwaccel_output_format, ic, st);
if (hwaccel_output_format) {
ist->hwaccel_output_format = av_get_pix_fmt(hwaccel_output_format);
if (ist->hwaccel_output_format == AV_PIX_FMT_NONE) {
av_log(NULL, AV_LOG_FATAL, "Unrecognised hwaccel output "
"format: %s", hwaccel_output_format);
}
} else {
ist->hwaccel_output_format = AV_PIX_FMT_NONE;
}
ist->hwaccel_pix_fmt = AV_PIX_FMT_NONE;
break;
case AVMEDIA_TYPE_AUDIO:
ist->guess_layout_max = INT_MAX;
MATCH_PER_STREAM_OPT(guess_layout_max, i, ist->guess_layout_max, ic, st);
guess_input_channel_layout(ist);// 设置通道布局到ist中
break;
case AVMEDIA_TYPE_DATA:
case AVMEDIA_TYPE_SUBTITLE: {
char *canvas_size = NULL;
if(!ist->dec)// 一般在choose_decoder时已经找到
ist->dec = avcodec_find_decoder(par->codec_id);
MATCH_PER_STREAM_OPT(fix_sub_duration, i, ist->fix_sub_duration, ic, st);