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ffmpeg.c
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ffmpeg.c
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/*
* Copyright (c) 2000-2003 Fabrice Bellard
*
* 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
*/
/**
* @file
* multimedia converter based on the FFmpeg libraries
*/
#include "config.h"
#include <ctype.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <stdatomic.h>
#include <stdint.h>
#if HAVE_IO_H
#include <io.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "libavformat/avformat.h"
#include "libavdevice/avdevice.h"
#include "libswresample/swresample.h"
#include "libavutil/opt.h"
#include "libavutil/channel_layout.h"
#include "libavutil/parseutils.h"
#include "libavutil/samplefmt.h"
#include "libavutil/fifo.h"
#include "libavutil/hwcontext.h"
#include "libavutil/internal.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/dict.h"
#include "libavutil/display.h"
#include "libavutil/mathematics.h"
#include "libavutil/pixdesc.h"
#include "libavutil/avstring.h"
#include "libavutil/libm.h"
#include "libavutil/imgutils.h"
#include "libavutil/timestamp.h"
#include "libavutil/bprint.h"
#include "libavutil/time.h"
#include "libavutil/thread.h"
#include "libavutil/threadmessage.h"
#include "libavcodec/mathops.h"
#include "libavformat/os_support.h"
# include "libavfilter/avfilter.h"
# include "libavfilter/buffersrc.h"
# include "libavfilter/buffersink.h"
#if HAVE_SYS_RESOURCE_H
#include <sys/time.h>
#include <sys/types.h>
#include <sys/resource.h>
#elif HAVE_GETPROCESSTIMES
#include <windows.h>
#endif
#if HAVE_GETPROCESSMEMORYINFO
#include <windows.h>
#include <psapi.h>
#endif
#if HAVE_SETCONSOLECTRLHANDLER
#include <windows.h>
#endif
#if HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#if HAVE_TERMIOS_H
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <termios.h>
#elif HAVE_KBHIT
#include <conio.h>
#endif
#include <time.h>
#include "ffmpeg.h"
#include "cmdutils.h"
#include "libavutil/avassert.h"
const char program_name[] = "ffmpeg";
const int program_birth_year = 2000;
static FILE *vstats_file;
const char *const forced_keyframes_const_names[] = {
"n",
"n_forced",
"prev_forced_n",
"prev_forced_t",
"t",
NULL
};
typedef struct BenchmarkTimeStamps {
int64_t real_usec; // transcode()调用前的实时时间，see av_gettime_relative().单位微秒
int64_t user_usec; // 进程在用户层消耗的时间.单位微秒
int64_t sys_usec; // 进程在内核层消耗的时间.单位微秒
} BenchmarkTimeStamps;
static void do_video_stats(OutputStream *ost, int frame_size);
static BenchmarkTimeStamps get_benchmark_time_stamps(void);
static int64_t getmaxrss(void);
static int ifilter_has_all_input_formats(FilterGraph *fg);
static int run_as_daemon = 0; // 0=前台运行；1=后台运行
static int nb_frames_dup = 0;
static unsigned dup_warning = 1000;
static int nb_frames_drop = 0;
static int64_t decode_error_stat[2];// 记录解码的状态.下标0记录的是成功解码的参数,下标1是失败的次数.
static int want_sdp = 1;
static BenchmarkTimeStamps current_time;
AVIOContext *progress_avio = NULL; // 指定-progress选项,会在回调为该全局对象初始化
static uint8_t *subtitle_out;
InputStream **input_streams = NULL;
int nb_input_streams = 0;
InputFile **input_files = NULL;
int nb_input_files = 0;
OutputStream **output_streams = NULL;
int nb_output_streams = 0;
OutputFile **output_files = NULL;
int nb_output_files = 0;
FilterGraph **filtergraphs;
int nb_filtergraphs;
#if HAVE_TERMIOS_H
/* init terminal so that we can grab keys */
static struct termios oldtty;
static int restore_tty;
#endif
#if HAVE_THREADS
static void free_input_threads(void);
#endif
/* sub2video hack:
Convert subtitles to video with alpha to insert them in filter graphs.
This is a temporary solution until libavfilter gets real subtitles support.
*/
static int sub2video_get_blank_frame(InputStream *ist)
{
int ret;
AVFrame *frame = ist->sub2video.frame;
av_frame_unref(frame);
ist->sub2video.frame->width = ist->dec_ctx->width ? ist->dec_ctx->width : ist->sub2video.w;
ist->sub2video.frame->height = ist->dec_ctx->height ? ist->dec_ctx->height : ist->sub2video.h;
ist->sub2video.frame->format = AV_PIX_FMT_RGB32;
if ((ret = av_frame_get_buffer(frame, 32)) < 0)
return ret;
memset(frame->data[0], 0, frame->height * frame->linesize[0]);
return 0;
}
static void sub2video_copy_rect(uint8_t *dst, int dst_linesize, int w, int h,
AVSubtitleRect *r)
{
uint32_t *pal, *dst2;
uint8_t *src, *src2;
int x, y;
if (r->type != SUBTITLE_BITMAP) {
av_log(NULL, AV_LOG_WARNING, "sub2video: non-bitmap subtitle\n");
return;
}
if (r->x < 0 || r->x + r->w > w || r->y < 0 || r->y + r->h > h) {
av_log(NULL, AV_LOG_WARNING, "sub2video: rectangle (%d %d %d %d) overflowing %d %d\n",
r->x, r->y, r->w, r->h, w, h
);
return;
}
dst += r->y * dst_linesize + r->x * 4;
src = r->data[0];
pal = (uint32_t *)r->data[1];
for (y = 0; y < r->h; y++) {
dst2 = (uint32_t *)dst;
src2 = src;
for (x = 0; x < r->w; x++)
*(dst2++) = pal[*(src2++)];
dst += dst_linesize;
src += r->linesize[0];
}
}
static void sub2video_push_ref(InputStream *ist, int64_t pts)
{
AVFrame *frame = ist->sub2video.frame;
int i;
int ret;
av_assert1(frame->data[0]);
ist->sub2video.last_pts = frame->pts = pts;
for (i = 0; i < ist->nb_filters; i++) {
ret = av_buffersrc_add_frame_flags(ist->filters[i]->filter, frame,
AV_BUFFERSRC_FLAG_KEEP_REF |
AV_BUFFERSRC_FLAG_PUSH);
if (ret != AVERROR_EOF && ret < 0)
av_log(NULL, AV_LOG_WARNING, "Error while add the frame to buffer source(%s).\n",
av_err2str(ret));
}
}
void sub2video_update(InputStream *ist, AVSubtitle *sub)
{
AVFrame *frame = ist->sub2video.frame;
int8_t *dst;
int dst_linesize;
int num_rects, i;
int64_t pts, end_pts;
if (!frame)
return;
if (sub) {
pts = av_rescale_q(sub->pts + sub->start_display_time * 1000LL,
AV_TIME_BASE_Q, ist->st->time_base);
end_pts = av_rescale_q(sub->pts + sub->end_display_time * 1000LL,
AV_TIME_BASE_Q, ist->st->time_base);
num_rects = sub->num_rects;
} else {
pts = ist->sub2video.end_pts;
end_pts = INT64_MAX;
num_rects = 0;
}
if (sub2video_get_blank_frame(ist) < 0) {
av_log(ist->dec_ctx, AV_LOG_ERROR,
"Impossible to get a blank canvas.\n");
return;
}
dst = frame->data [0];
dst_linesize = frame->linesize[0];
for (i = 0; i < num_rects; i++)
sub2video_copy_rect(dst, dst_linesize, frame->width, frame->height, sub->rects[i]);
sub2video_push_ref(ist, pts);
ist->sub2video.end_pts = end_pts;
}
static void sub2video_heartbeat(InputStream *ist, int64_t pts)
{
InputFile *infile = input_files[ist->file_index];
int i, j, nb_reqs;
int64_t pts2;
/* When a frame is read from a file, examine all sub2video streams in
the same file and send the sub2video frame again. Otherwise, decoded
video frames could be accumulating in the filter graph while a filter
(possibly overlay) is desperately waiting for a subtitle frame. */
for (i = 0; i < infile->nb_streams; i++) {
InputStream *ist2 = input_streams[infile->ist_index + i];
if (!ist2->sub2video.frame)
continue;
/* subtitles seem to be usually muxed ahead of other streams;
if not, subtracting a larger time here is necessary */
pts2 = av_rescale_q(pts, ist->st->time_base, ist2->st->time_base) - 1;
/* do not send the heartbeat frame if the subtitle is already ahead */
if (pts2 <= ist2->sub2video.last_pts)
continue;
if (pts2 >= ist2->sub2video.end_pts ||
(!ist2->sub2video.frame->data[0] && ist2->sub2video.end_pts < INT64_MAX))
sub2video_update(ist2, NULL);
for (j = 0, nb_reqs = 0; j < ist2->nb_filters; j++)
nb_reqs += av_buffersrc_get_nb_failed_requests(ist2->filters[j]->filter);
if (nb_reqs)
sub2video_push_ref(ist2, pts2);
}
}
static void sub2video_flush(InputStream *ist)
{
int i;
int ret;
if (ist->sub2video.end_pts < INT64_MAX)
sub2video_update(ist, NULL);
for (i = 0; i < ist->nb_filters; i++) {
ret = av_buffersrc_add_frame(ist->filters[i]->filter, NULL);
if (ret != AVERROR_EOF && ret < 0)
av_log(NULL, AV_LOG_WARNING, "Flush the frame error.\n");
}
}
/* end of sub2video hack */
static void term_exit_sigsafe(void)
{
#if HAVE_TERMIOS_H
if(restore_tty)
tcsetattr (0, TCSANOW, &oldtty);
#endif
}
void term_exit(void)
{
av_log(NULL, AV_LOG_QUIET, "%s", "");
term_exit_sigsafe();
}
static volatile int received_sigterm = 0;
static volatile int received_nb_signals = 0;
static atomic_int transcode_init_done = ATOMIC_VAR_INIT(0);
static volatile int ffmpeg_exited = 0;
static int main_return_code = 0;
static void
sigterm_handler(int sig)
{
int ret;
received_sigterm = sig;
received_nb_signals++;
term_exit_sigsafe();
if(received_nb_signals > 3) {
ret = write(2/*STDERR_FILENO*/, "Received > 3 system signals, hard exiting\n",
strlen("Received > 3 system signals, hard exiting\n"));
if (ret < 0) { /* Do nothing */ };
exit(123);
}
}
#if HAVE_SETCONSOLECTRLHANDLER
static BOOL WINAPI CtrlHandler(DWORD fdwCtrlType)
{
av_log(NULL, AV_LOG_DEBUG, "\nReceived windows signal %ld\n", fdwCtrlType);
switch (fdwCtrlType)
{
case CTRL_C_EVENT:
case CTRL_BREAK_EVENT:
sigterm_handler(SIGINT);
return TRUE;
case CTRL_CLOSE_EVENT:
case CTRL_LOGOFF_EVENT:
case CTRL_SHUTDOWN_EVENT:
sigterm_handler(SIGTERM);
/* Basically, with these 3 events, when we return from this method the
process is hard terminated, so stall as long as we need to
to try and let the main thread(s) clean up and gracefully terminate
(we have at most 5 seconds, but should be done far before that). */
while (!ffmpeg_exited) {
Sleep(0);
}
return TRUE;
default:
av_log(NULL, AV_LOG_ERROR, "Received unknown windows signal %ld\n", fdwCtrlType);
return FALSE;
}
}
#endif
void term_init(void)
{
#if HAVE_TERMIOS_H
if (!run_as_daemon && stdin_interaction) {
struct termios tty;
if (tcgetattr (0, &tty) == 0) {
oldtty = tty;
restore_tty = 1;
tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP
|INLCR|IGNCR|ICRNL|IXON);
tty.c_oflag |= OPOST;
tty.c_lflag &= ~(ECHO|ECHONL|ICANON|IEXTEN);
tty.c_cflag &= ~(CSIZE|PARENB);
tty.c_cflag |= CS8;
tty.c_cc[VMIN] = 1;
tty.c_cc[VTIME] = 0;
tcsetattr (0, TCSANOW, &tty);
}
signal(SIGQUIT, sigterm_handler); /* Quit (POSIX). */
}
#endif
signal(SIGINT , sigterm_handler); /* Interrupt (ANSI). */
signal(SIGTERM, sigterm_handler); /* Termination (ANSI). */
#ifdef SIGXCPU
signal(SIGXCPU, sigterm_handler);
#endif
#ifdef SIGPIPE
signal(SIGPIPE, SIG_IGN); /* Broken pipe (POSIX). */
#endif
#if HAVE_SETCONSOLECTRLHANDLER
SetConsoleCtrlHandler((PHANDLER_ROUTINE) CtrlHandler, TRUE);
#endif
}
/* read a key without blocking */
static int read_key(void)
{
unsigned char ch;
#if HAVE_TERMIOS_H
int n = 1;
struct timeval tv;
fd_set rfds;
FD_ZERO(&rfds);
FD_SET(0, &rfds);
tv.tv_sec = 0;
tv.tv_usec = 0;
n = select(1, &rfds, NULL, NULL, &tv);
if (n > 0) {
n = read(0, &ch, 1);
if (n == 1)
return ch;
return n;
}
#elif HAVE_KBHIT
# if HAVE_PEEKNAMEDPIPE
static int is_pipe;
static HANDLE input_handle;
DWORD dw, nchars;
// 1. 获取输入句柄，并且获取控制台模式(不过ffmpeg没有对控制台模式进一步处理).
if(!input_handle){
//获取输入设备的句柄.GetStdHandle see https://blog.csdn.net/dark_cy/article/details/89103875
input_handle = GetStdHandle(STD_INPUT_HANDLE);
/*GetConsoleMode() see https://docs.microsoft.com/en-us/windows/console/getconsolemode.
返回0表示错误；非0成功.*/
is_pipe = !GetConsoleMode(input_handle, &dw);//获取控制台模式 see https://blog.csdn.net/zanglengyu/article/details/125855938
}
// 2. 获取控制台模式失败的处理
if (is_pipe) {
/* When running under a GUI, you will end here.(当在GUI下运行时，您将在这里结束) */
/* PeekNamedPipe()：从句柄的缓冲区读取数据，若不想读取，参2传NULL即可.管道不存在会报错返回0。
* msdn：https://docs.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-peeknamedpipe
* see http://www.manongjc.com/detail/19-xpsioohwzlyyvpp.html的例子*/
if (!PeekNamedPipe(input_handle, NULL, 0, NULL, &nchars, NULL)) {//nchars是读到的字节数
// input pipe may have been closed by the program that ran ffmpeg
//(输入管道可能已被运行ffmpeg的程序关闭)
return -1;
}
//Read it
if(nchars != 0) {
read(0, &ch, 1);
return ch;
}else{
return -1;
}
}
# endif
if(kbhit())
return(getch());
#endif
return -1;
}
static int decode_interrupt_cb(void *ctx)
{
return received_nb_signals > atomic_load(&transcode_init_done);
}
const AVIOInterruptCB int_cb = { decode_interrupt_cb, NULL };
static void ffmpeg_cleanup(int ret)
{
int i, j;
if (do_benchmark) {
int maxrss = getmaxrss() / 1024;
av_log(NULL, AV_LOG_INFO, "bench: maxrss=%ikB\n", maxrss);
}
// 1. 释放fg数组相关内容
for (i = 0; i < nb_filtergraphs; i++) {
FilterGraph *fg = filtergraphs[i];
// 1.1 释放滤波图
avfilter_graph_free(&fg->graph);
// 1.2 释放InputFilter数组
for (j = 0; j < fg->nb_inputs; j++) {
while (av_fifo_size(fg->inputs[j]->frame_queue)) {// 释放帧队列剩余的帧
AVFrame *frame;
av_fifo_generic_read(fg->inputs[j]->frame_queue, &frame,
sizeof(frame), NULL);
av_frame_free(&frame);
}
av_fifo_freep(&fg->inputs[j]->frame_queue);
if (fg->inputs[j]->ist->sub2video.sub_queue) {
while (av_fifo_size(fg->inputs[j]->ist->sub2video.sub_queue)) {
AVSubtitle sub;
av_fifo_generic_read(fg->inputs[j]->ist->sub2video.sub_queue,
&sub, sizeof(sub), NULL);
avsubtitle_free(&sub);
}
av_fifo_freep(&fg->inputs[j]->ist->sub2video.sub_queue);
}
av_buffer_unref(&fg->inputs[j]->hw_frames_ctx);
av_freep(&fg->inputs[j]->name);
av_freep(&fg->inputs[j]);
}
av_freep(&fg->inputs);
// 1.3 释放OutputFilter数组
for (j = 0; j < fg->nb_outputs; j++) {
av_freep(&fg->outputs[j]->name);
av_freep(&fg->outputs[j]->formats);
av_freep(&fg->outputs[j]->channel_layouts);
av_freep(&fg->outputs[j]->sample_rates);
av_freep(&fg->outputs[j]);
}
av_freep(&fg->outputs);
av_freep(&fg->graph_desc);
// 1.4 释放fg元素
av_freep(&filtergraphs[i]);
}
// 1.5 释放fg数组本身
av_freep(&filtergraphs);
av_freep(&subtitle_out);
// 2. 关闭输出文件
/* close files */
for (i = 0; i < nb_output_files; i++) {
OutputFile *of = output_files[i];
AVFormatContext *s;
if (!of)
continue;
s = of->ctx;
if (s && s->oformat && !(s->oformat->flags & AVFMT_NOFILE))
avio_closep(&s->pb);
avformat_free_context(s);
av_dict_free(&of->opts);
av_freep(&output_files[i]);
}
// 3. 关闭输出流
for (i = 0; i < nb_output_streams; i++) {
OutputStream *ost = output_streams[i];
if (!ost)
continue;
for (j = 0; j < ost->nb_bitstream_filters; j++)
av_bsf_free(&ost->bsf_ctx[j]);
av_freep(&ost->bsf_ctx);
av_frame_free(&ost->filtered_frame);
av_frame_free(&ost->last_frame);
av_dict_free(&ost->encoder_opts);
av_freep(&ost->forced_keyframes);
av_expr_free(ost->forced_keyframes_pexpr);
av_freep(&ost->avfilter);
av_freep(&ost->logfile_prefix);
av_freep(&ost->audio_channels_map);
ost->audio_channels_mapped = 0;
av_dict_free(&ost->sws_dict);
av_dict_free(&ost->swr_opts);
avcodec_free_context(&ost->enc_ctx);// 释放编码器上下文
avcodec_parameters_free(&ost->ref_par);
if (ost->muxing_queue) {
while (av_fifo_size(ost->muxing_queue)) {
AVPacket pkt;
av_fifo_generic_read(ost->muxing_queue, &pkt, sizeof(pkt), NULL);
av_packet_unref(&pkt);
}
av_fifo_freep(&ost->muxing_queue);
}
av_freep(&output_streams[i]);
}
// 4. 回收输入线程
#if HAVE_THREADS
free_input_threads();
#endif
// 5. 关闭输入文件
for (i = 0; i < nb_input_files; i++) {
avformat_close_input(&input_files[i]->ctx);
av_freep(&input_files[i]);
}
// 6. 关闭输入流
for (i = 0; i < nb_input_streams; i++) {
InputStream *ist = input_streams[i];
av_frame_free(&ist->decoded_frame);
av_frame_free(&ist->filter_frame);
av_dict_free(&ist->decoder_opts);
avsubtitle_free(&ist->prev_sub.subtitle);
av_frame_free(&ist->sub2video.frame);
av_freep(&ist->filters);
av_freep(&ist->hwaccel_device);
av_freep(&ist->dts_buffer);
avcodec_free_context(&ist->dec_ctx);// 关闭解码器上下文
av_freep(&input_streams[i]);
}
if (vstats_file) {
if (fclose(vstats_file))
av_log(NULL, AV_LOG_ERROR,
"Error closing vstats file, loss of information possible: %s\n",
av_err2str(AVERROR(errno)));
}
av_freep(&vstats_filename);
// 7. 关闭输入输出文件、流数组本身.
av_freep(&input_streams);
av_freep(&input_files);
av_freep(&output_streams);
av_freep(&output_files);
uninit_opts();
avformat_network_deinit();
if (received_sigterm) {
av_log(NULL, AV_LOG_INFO, "Exiting normally, received signal %d.\n",
(int) received_sigterm);
} else if (ret && atomic_load(&transcode_init_done)) {
av_log(NULL, AV_LOG_INFO, "Conversion failed!\n");
}
term_exit();
ffmpeg_exited = 1;
}
/**
* @brief 利用b中的key，将a中有同样key的value设置为NULL.获取时忽略后缀，设置时匹配大小写.
* @param a 字典1
* @param b 字典2
*/
void remove_avoptions(AVDictionary **a, AVDictionary *b)
{
AVDictionaryEntry *t = NULL;
while ((t = av_dict_get(b, "", t, AV_DICT_IGNORE_SUFFIX))) {
av_dict_set(a, t->key, NULL, AV_DICT_MATCH_CASE);
}
}
/**
* @brief 只有m中还有一个k-v键值对选项，那么程序就会退出.
*/
void assert_avoptions(AVDictionary *m)
{
AVDictionaryEntry *t;
if ((t = av_dict_get(m, "", NULL, AV_DICT_IGNORE_SUFFIX))) {
av_log(NULL, AV_LOG_FATAL, "Option %s not found.\n", t->key);
exit_program(1);
}
}
static void abort_codec_experimental(AVCodec *c, int encoder)
{
exit_program(1);
}
static void update_benchmark(const char *fmt, ...)
{
if (do_benchmark_all) {
BenchmarkTimeStamps t = get_benchmark_time_stamps();
va_list va;
char buf[1024];
if (fmt) {
va_start(va, fmt);
vsnprintf(buf, sizeof(buf), fmt, va);
va_end(va);
av_log(NULL, AV_LOG_INFO,
"bench: %8" PRIu64 " user %8" PRIu64 " sys %8" PRIu64 " real %s \n",
t.user_usec - current_time.user_usec,
t.sys_usec - current_time.sys_usec,
t.real_usec - current_time.real_usec, buf);
}
current_time = t;
}
}
/**
* @brief 给输出流退出时进行标记。
* @param ost 输出流
* @param this_stream ost的标记
* @param others ost以外的其它输出流的标记
* @note 并不是真正关闭输出流
*/
static void close_all_output_streams(OutputStream *ost, OSTFinished this_stream, OSTFinished others)
{
int i;
for (i = 0; i < nb_output_streams; i++) {
OutputStream *ost2 = output_streams[i];
ost2->finished |= ost == ost2 ? this_stream : others;
}
}
/**
* @brief 将pkt写到输出文件(可以是文件或者实时流地址)
* @param of 输出文件
* @param pkt pkt
* @param ost 输出流
* @param unqueue 是否已经计算该pkt在ost->frame_number中,=1表示已经计算。see check_init_output_file()
*/
static void write_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost, int unqueue)
{
AVFormatContext *s = of->ctx;
AVStream *st = ost->st;
int ret;
/*
* Audio encoders may split the packets -- #frames in != #packets out.
* But there is no reordering, so we can limit the number of output packets
* by simply dropping them here.
* Counting encoded video frames needs to be done separately because of
* reordering, see do_video_out().
* Do not count the packet when unqueued because it has been counted when queued.
*/
/*
* 音频编码器可能会分割数据包 -- #输入帧!= #输出包。
* 但是没有重新排序，所以我们可以通过简单地将它们放在这里来限制输出数据包的数量。
* 由于重新排序，编码的视频帧需要单独计数，参见do_video_out()。
* 不要在未排队时计数数据包，因为它在排队时已被计数。
*/
/* 1. 统计已经写帧的数量. */
// "视频需要编码"以外的类型，且unqueue=0表示该pkt没有计算时，会进行计算.
if (!(st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && ost->encoding_needed) && !unqueue) {
if (ost->frame_number >= ost->max_frames) {// 帧数大于允许的最大帧数，不作处理，并将该包释放
av_packet_unref(pkt);
return;
}
ost->frame_number++;// 视频流需要编码时，不会在这里计数，会在do_video_out()单独计数
#ifdef TYYCODE_TIMESTAMP_MUXER
mydebug(NULL, AV_LOG_INFO, "write_packet(), tpye: %s, ost->frame_number: %d\n",
av_get_media_type_string(st->codecpar->codec_type), ost->frame_number);
#endif
}
/* 2.没有写头或者写头失败，先将包缓存在复用队列，然后返回，不会调用到写帧函数 */
if (!of->header_written) {
AVPacket tmp_pkt = {0};
/* the muxer is not initialized yet, buffer the packet(muxer尚未初始化，请缓冲该数据包) */
// 2.1 fifo没有空间，则给其扩容
if (!av_fifo_space(ost->muxing_queue)) {// return f->end - f->buffer - av_fifo_size(f);
/* 新队列大小求法：若在最大队列大小内，那么以当前队列大小的两倍扩容.
* 例如用户不指定大小，默认是给复用队列先开辟8个空间大小，若此时没空间，说明av_fifo_size()返回的值为8*sizeof(pkt)，
* 那么乘以2后，new_size值就是16个pkt的大小了. */
int new_size = FFMIN(2 * av_fifo_size(ost->muxing_queue),
ost->max_muxing_queue_size);
/* 若输出流的包缓存到达最大复用队列，那么ffmpeg会退出程序 */
if (new_size <= av_fifo_size(ost->muxing_queue)) {
av_log(NULL, AV_LOG_ERROR,
"Too many packets buffered for output stream %d:%d.\n",
ost->file_index, ost->st->index);
exit_program(1);
}
ret = av_fifo_realloc2(ost->muxing_queue, new_size);
if (ret < 0)
exit_program(1);
}
/*
* av_packet_make_refcounted(): 确保给定数据包所描述的数据被引用计数。
* @note 此函数不确保引用是可写的。 为此使用av_packet_make_writable。
* @see av_packet_ref.
* @see av_packet_make_writable.
* @param pkt 计算需要参考的PKT数据包.
* @return 成功为0，错误为负AVERROR。失败时，数据包不变。
* 源码也不难，工作是：
* 拷贝packet数据到pkt->buf->data中，再令pkt->data指向它.
*/
ret = av_packet_make_refcounted(pkt);
if (ret < 0)
exit_program(1);
av_packet_move_ref(&tmp_pkt, pkt);// 所有权转移，源码很简单
/*
* av_fifo_generic_write(): 将数据从用户提供的回调提供给AVFifoBuffer。
* @param f 要写入的AVFifoBuffer.
* @param src 数据来源;非const，因为它可以被定义在func中的函数用作可修改的上下文.
* @param size 要写入的字节数.
* @param func 一般写函数;第一个参数是src，第二个参数是dest_buf，第三个参数是dest_buf_size.
* Func必须返回写入dest_buf的字节数，或<= 0表示没有更多可写入的数据。如果func为NULL, src将被解释为源数据的简单字节数组。
* @return 写入FIFO的字节数.
* av_fifo_generic_write()的源码不算难.
*/
av_fifo_generic_write(ost->muxing_queue, &tmp_pkt, sizeof(tmp_pkt), NULL);
return;
}
// 3. 将pkt.pts/pkt.dts置为无效值
if ((st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && video_sync_method == VSYNC_DROP) ||
(st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO && audio_sync_method < 0))
pkt->pts = pkt->dts = AV_NOPTS_VALUE;
// 4. 获取该pkt的编码质量,图片类型等信息.
if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
int i;
// 关于下面获取q编码质量可参考https://blog.csdn.net/u012117034/article/details/123453863
/*
* av_packet_get_side_data():从packet获取side info.
* @param type 期待side information的类型
* @param size 用于存储side info大小的指针(可选)
* @return 如果存在数据，则指向数据的指针，否则为NULL.
* 源码很简单.
*/
// 获取编码质量状态的side data info
uint8_t *sd = av_packet_get_side_data(pkt, AV_PKT_DATA_QUALITY_STATS,
NULL);
// 从sd中获取前32bit
/* AV_RL32(sd)的大概调用过程：
* 1)AV_RL(32, p)
* 2）而AV_RL的定义：
* # define AV_RL(s, p) AV_RN##s(p)
* 3）所以此时调用变成(##表示将参数与前后拼接)：
* AV_RN32(p)
* 4）而AV_RN32的定义：
* # define AV_RN32(p) AV_RN(32, p)
* 5）而AV_RN的定义：
* # define AV_RN(s, p) (*((const __unaligned uint##s##_t*)(p)))
* 所以最终就是取sd前32bit的内容.(这部分是我使用vscode看源码得出的，qt貌似会跳转的共用体，不太准？)
*
* 至于为什么要获取32bit，看AV_PKT_DATA_QUALITY_STATS枚举注释，这个信息会由编码器填充，
* 被放在side info的前32bit，然后第5个字节存放帧类型，第6个字节存放错误次数，
* 第7、8两字节为保留位，
* 后面剩余的u64le[error count]是一个数组,每个元素是8字节.
*/
ost->quality = sd ? AV_RL32(sd) : -1;
ost->pict_type = sd ? sd[4] : AV_PICTURE_TYPE_NONE;
#ifdef TYYCODE_TIMESTAMP_MUXER
mydebug(NULL, AV_LOG_INFO, "write_packet(), video, ost->quality: %d, ost->pict_type: %c\n",
ost->quality, av_get_picture_type_char((enum AVPictureType)ost->pict_type));
#endif
for (i = 0; i<FF_ARRAY_ELEMS(ost->error); i++) {// ost->error[4]数组大小是4，i可能是0-4的值,即最多保存近4次的错误
if (sd && i < sd[5])// 若错误次数(error count) 大于0次以上，即表示有错误
ost->error[i] = AV_RL64(sd + 8 + 8*i);// sd+8是跳过quality+pict_type+保留位，8*i表示跳过前面已经获取的错误.
else
ost->error[i] = -1;// 没有错误
}
// 是否通过帧率对duration重写
if (ost->frame_rate.num && ost->is_cfr) {
// (通过帧速率覆盖数据包持续时间，这应该不会发生)
if (pkt->duration > 0)
av_log(NULL, AV_LOG_WARNING, "Overriding packet duration by frame rate, this should not happen\n");
pkt->duration = av_rescale_q(1, av_inv_q(ost->frame_rate),
ost->mux_timebase);
}
}
// 5. 将pkt相关的时间戳转成输出容器的时基
/* 内部调用av_rescale_q，将pkt里面与时间戳相关的pts、dts、duration、convergence_duration转成以ost->st->time_base为单位 */
av_packet_rescale_ts(pkt, ost->mux_timebase, ost->st->time_base);
#ifdef TYYCODE_TIMESTAMP_MUXER
mydebug(NULL, AV_LOG_WARNING, "write_packet(), ost->mux_timebase: %d/%d, "
"ost->st->time_base: %d/%d, "
"output stream %d:%d\n",
ost->mux_timebase.num, ost->mux_timebase.den,
ost->st->time_base.num, ost->st->time_base.den,
ost->file_index, ost->st->index);
#endif
/* 6. 输出流需要有时间戳的处理 */
/* AVFMT_NOTIMESTAMPS: 格式不需要/有任何时间戳.
* 所以当没有该宏时，就说明需要时间戳 */
if (!(s->oformat->flags & AVFMT_NOTIMESTAMPS)) {
// 6.1 解码时间戳比显示时间戳大，重写它们的时间戳
if (pkt->dts != AV_NOPTS_VALUE &&
pkt->pts != AV_NOPTS_VALUE &&
pkt->dts > pkt->pts) {
av_log(s, AV_LOG_WARNING, "Invalid DTS: %"PRId64" PTS: %"PRId64" in output stream %d:%d, replacing by guess\n",
pkt->dts, pkt->pts,
ost->file_index, ost->st->index);
pkt->pts =
pkt->dts = pkt->pts + pkt->dts + ost->last_mux_dts + 1
- FFMIN3(pkt->pts, pkt->dts, ost->last_mux_dts + 1)
- FFMAX3(pkt->pts, pkt->dts, ost->last_mux_dts + 1);// 减去最大最小值，最终得到的就是三者之中，处于中间的那个值
#ifdef TYYCODE_TIMESTAMP_MUXER
mydebug(NULL, AV_LOG_WARNING, "write_packet(), pkt->dts: %"PRId64", pkt->pts: %"PRId64", ost->last_mux_dts + 1: %"PRId64", "
"output stream %d:%d\n", pkt->dts, pkt->pts, ost->last_mux_dts + 1, ost->file_index, ost->st->index);
#endif
}
/* 6.2 判断当前pkt.dts与上一个pkt.dts比是否单调递增,以此修正pkt的pts/dts */
if ((st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO || st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO || st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE) &&
pkt->dts != AV_NOPTS_VALUE &&
!(st->codecpar->codec_id == AV_CODEC_ID_VP9 && ost->stream_copy) && /* VP9且不转码以外的条件 */
ost->last_mux_dts != AV_NOPTS_VALUE) {
/* AVFMT_TS_NONSTRICT：格式不需要严格增加时间戳，但它们仍然必须是单调的 */
// 包含该宏,max是last_mux_dts; 不包含,max是last_mux_dts+1.加1主要是确保单调递增.
int64_t max = ost->last_mux_dts + !(s->oformat->flags & AVFMT_TS_NONSTRICT);
#ifdef TYYCODE_TIMESTAMP_MUXER
mydebug(NULL, AV_LOG_INFO, "write_packet(), --, "
"pkt->dts: %"PRId64", pkt->pts: %"PRId64", ost->last_mux_dts + 1: %"PRId64", ""max, "
"%"PRId64",output stream %d:%d\n",
pkt->dts, pkt->pts, ost->last_mux_dts + 1, max,
ost->file_index, ost->st->index);
#endif
if (pkt->dts < max) {
int loglevel = max - pkt->dts > 2 || st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO ? AV_LOG_WARNING : AV_LOG_DEBUG;
av_log(s, loglevel, "Non-monotonous DTS in output stream "
"%d:%d; previous: %"PRId64", current: %"PRId64"; ",
ost->file_index, ost->st->index, ost->last_mux_dts, pkt->dts);// dts没有单调递增
if (exit_on_error) {//-xerror选项，默认是0
av_log(NULL, AV_LOG_FATAL, "aborting.\n");
exit_program(1);
}
av_log(s, loglevel, "changing to %"PRId64". This may result "
"in incorrect timestamps in the output file.\n",
max);// (这可能会导致输出文件中的时间戳不正确)
#ifdef TYYCODE_TIMESTAMP_MUXER
mydebug(NULL, AV_LOG_INFO, "write_packet(), pkt->dts < max\n");
#endif
if (pkt->pts >= pkt->dts)
pkt->pts = FFMAX(pkt->pts, max);
pkt->dts = max;
}
}
}
ost->last_mux_dts = pkt->dts; // 保存最近一次有效的dts
ost->data_size += pkt->size; // 统计所有写入的包的字节大小
ost->packets_written++; // 统计所有写入的包的个数
pkt->stream_index = ost->index;
if (debug_ts) {// -debug_ts选项
av_log(NULL, AV_LOG_INFO, "muxer <- type:%s "
"pkt_pts:%s pkt_pts_time:%s pkt_dts:%s pkt_dts_time:%s size:%d\n",
av_get_media_type_string(ost->enc_ctx->codec_type),
av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &ost->st->time_base),
av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &ost->st->time_base),
pkt->size
);
}
// 7. 写帧
ret = av_interleaved_write_frame(s, pkt);
if (ret < 0) {
print_error("av_interleaved_write_frame()", ret);
main_return_code = 1;
close_all_output_streams(ost, MUXER_FINISHED | ENCODER_FINISHED, ENCODER_FINISHED);
}
av_packet_unref(pkt);
}
/**
* @brief 给该输出流标记ENCODER_FINISHED.
* @param ost 输出流
*/
static void close_output_stream(OutputStream *ost)
{
OutputFile *of = output_files[ost->file_index];
ost->finished |= ENCODER_FINISHED;
if (of->shortest) {//重新设置录像时长.
int64_t end = av_rescale_q(ost->sync_opts - ost->first_pts, ost->enc_ctx->time_base, AV_TIME_BASE_Q);
of->recording_time = FFMIN(of->recording_time, end);
}
}