ffplay程序运行流程分析
2013-12-30 10:58
393 查看
/article/11042214.html
1、main()开始：
分别注册编解码器，复用以及解复用器
[cpp] view
plaincopyprint?
avcodec_register_all(); //register codec
avdevice_register_all();
av_register_all(); //register demux and mux
接着就是一些分配内存空间的代码
代码 略
[csharp] view
plaincopyprint?
parse_options(argc, argv, options, opt_input_file); //分析是否带有选项？
flags = SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER; //设置SDL的参数，我们选择了显示图像声音，并注册了一个定时器
SDL_Init (flags) <span style="white-space:pre"> </span>//初始化SDL
SDL_EventState(SDL_ACTIVEEVENT, SDL_IGNORE); //设置SDL的响应事件
SDL_EventState(SDL_MOUSEMOTION, SDL_IGNORE);
SDL_EventState(SDL_SYSWMEVENT, SDL_IGNORE);
SDL_EventState(SDL_USEREVENT, SDL_IGNORE);
av_init_packet(&flush_pkt); //初始化一个AVPacket
这个是重点：
[csharp] view
plaincopyprint?
cur_stream = stream_open(input_filename, file_iformat); //打开一个流，可以是file,tcp,rtp,udp,http等
2、具体分析stream_open()函数：
首先初始化了显示视频要的互斥锁，条件变量
[csharp] view
plaincopyprint?
is->pictq_mutex = SDL_CreateMutex();
is->pictq_cond = SDL_CreateCond();
is->subpq_mutex = SDL_CreateMutex();
is->subpq_cond = SDL_CreateCond();
/* add the refresh timer to draw the picture */
schedule_refresh(is, 40);
is->parse_tid = SDL_CreateThread(decode_thread, is); //创建解码线程
stream_open()函数调用结束。
3、接着分析decode_thread线程：
开始会初始化VideoState的部分参数
[csharp] view
plaincopyprint?
static int decode_thread(void *arg)
{
VideoState *is = arg;
AVFormatContext *ic;
int err, i, ret, video_index, audio_index, subtitle_index;
AVPacket pkt1, *pkt = &pkt1;
AVFormatParameters params, *ap = ¶ms;
video_index = -1;
audio_index = -1;
subtitle_index = -1;
is->video_stream = -1;
is->audio_stream = -1;
is->subtitle_stream = -1;
global_video_state = is;
url_set_interrupt_cb(decode_interrupt_cb);
memset(ap, 0, sizeof(*ap));
ap->width = frame_width;
ap->height= frame_height;
ap->time_base= (AVRational){1, 25};
ap->pix_fmt = frame_pix_fmt;
err = av_open_input_file(&ic, is->filename, is->iformat, 0, ap); //要求打开文件或流
if (err < 0) {
print_error(is->filename, err);
ret = -1;
goto fail;
}
is->ic = ic;
if(genpts)
ic->flags |= AVFMT_FLAG_GENPTS;
err = av_find_stream_info(ic); //从文件中找到媒体即填充AVFormatContext结构体
if (err < 0) {
fprintf(stderr, "%s: could not find codec parameters\n", is->filename);
ret = -1;
goto fail;
}
if(ic->pb)
ic->pb->eof_reached= 0; //FIXME hack, ffplay maybe should not use url_feof() to test for the end
/* if seeking requested, we execute it */
if (start_time != AV_NOPTS_VALUE) {
int64_t timestamp;
timestamp = start_time;
/* add the stream start time */
if (ic->start_time != AV_NOPTS_VALUE)
timestamp += ic->start_time;
ret = av_seek_frame(ic, -1, timestamp, AVSEEK_FLAG_BACKWARD);
if (ret < 0) {
fprintf(stderr, "%s: could not seek to position %0.3f\n",
is->filename, (double)timestamp / AV_TIME_BASE);
}
}
for(i = 0; i < ic->nb_streams; i++) { //从流中探测是否有音频流和视频流,字幕流，并将找到的流ID赋值给video
AVCodecContext *enc = ic->streams[i]->codec;//_index,探测完所有的流后，退出
ic->streams[i]->discard = AVDISCARD_ALL;
switch(enc->codec_type) {
case CODEC_TYPE_AUDIO:
if (wanted_audio_stream-- >= 0 && !audio_disable)
audio_index = i; //found audio stream
break;
case CODEC_TYPE_VIDEO:
if (wanted_video_stream-- >= 0 && !video_disable)
video_index = i; //founf video stream
break;
case CODEC_TYPE_SUBTITLE:
if (wanted_subtitle_stream-- >= 0 && !video_disable)
subtitle_index = i; //found subtile stream
break;
default:
break;
}
}
if (show_status) {
dump_format(ic, 0, is->filename, 0);//
dump_stream_info(ic);
}
/* open the streams */
if (audio_index >= 0) {
stream_component_open(is, audio_index); //此函数里，会新建一个解码线程，用于音频解码
}
if (video_index >= 0) {
stream_component_open(is, video_index); //此函数里，会新建一个解码线程，用于视频解码
} else {
if (!display_disable)
is->show_audio = 1;
}
if (subtitle_index >= 0) {
stream_component_open(is, subtitle_index);
}
if (is->video_stream < 0 && is->audio_stream < 0) {
fprintf(stderr, "%s: could not open codecs\n", is->filename);
ret = -1;
goto fail;
}
for(;;) {
if (is->abort_request)
break;
if (is->paused != is->last_paused) {
is->last_paused = is->paused;
if (is->paused)
av_read_pause(ic);
else
av_read_play(ic);
}
#if CONFIG_RTSP_DEMUXER
if (is->paused && !strcmp(ic->iformat->name, "rtsp")) {
/* wait 10 ms to avoid trying to get another packet */
/* XXX: horrible */
SDL_Delay(10);
continue;
}
#endif
if (is->seek_req) {
int stream_index= -1;
int64_t seek_target= is->seek_pos;
if (is-> video_stream >= 0) stream_index= is-> video_stream;
else if(is-> audio_stream >= 0) stream_index= is-> audio_stream;
else if(is->subtitle_stream >= 0) stream_index= is->subtitle_stream;
if(stream_index>=0){
seek_target= av_rescale_q(seek_target, AV_TIME_BASE_Q, ic->streams[stream_index]->time_base); //av_rescale_q(a,b,c)是用来把时间戳从一个时基调整到另外一个时基时候用的函数
}
ret = av_seek_frame(is->ic, stream_index, seek_target, is->seek_flags); //移动IC的指针(实现快进快退的功能)
if (ret < 0) {
fprintf(stderr, "%s: error while seeking\n", is->ic->filename);
}else{
if (is->audio_stream >= 0) {
packet_queue_flush(&is->audioq); //清空pkt队列缓冲区 ，这是因为is->seek_req==1,用户要实现视频片段的跳转。在跳转到一个新的片段时，之前的缓冲区需要清空
packet_queue_put(&is->audioq, &flush_pkt); //队列已经被清空，需要将flush_pkt包(清空包)加入到队列，相当于一个链表的header(这样说不知道是不是正确)
}
if (is->subtitle_stream >= 0) {
packet_queue_flush(&is->subtitleq);
packet_queue_put(&is->subtitleq, &flush_pkt);
}
if (is->video_stream >= 0) {
packet_queue_flush(&is->videoq);
packet_queue_put(&is->videoq, &flush_pkt);
}
}
is->seek_req = 0;
}
/* if the queue are full, no need to read more */
if (is->audioq.size > MAX_AUDIOQ_SIZE ||
is->videoq.size > MAX_VIDEOQ_SIZE ||
is->subtitleq.size > MAX_SUBTITLEQ_SIZE) {
/* wait 10 ms */
SDL_Delay(10);
continue;
}
if(url_feof(ic->pb)) {
av_init_packet(pkt);
pkt->data=NULL;
pkt->size=0;
pkt->stream_index= is->video_stream;
packet_queue_put(&is->videoq, pkt);
continue;
}
ret = av_read_frame(ic, pkt); //读取一帧数据到pkt
if (ret < 0) {
if (ret != AVERROR_EOF && url_ferror(ic->pb) == 0) {
SDL_Delay(100); /* wait for user event */
continue;
} else
break;
}
if (pkt->stream_index == is->audio_stream) { //如果该帧为音频帧，则将该包加入到音频队列中
packet_queue_put(&is->audioq, pkt);
} else if (pkt->stream_index == is->video_stream) {
packet_queue_put(&is->videoq, pkt);
} else if (pkt->stream_index == is->subtitle_stream) {
packet_queue_put(&is->subtitleq, pkt);
} else {
av_free_packet(pkt); //如果不为以上的包，则释放该包。
}
}
/* wait until the end */
while (!is->abort_request) {
SDL_Delay(100);
}
ret = 0;
fail:
/* disable interrupting */
global_video_state = NULL;
/* close each stream */
if (is->audio_stream >= 0)
stream_component_close(is, is->audio_stream);
if (is->video_stream >= 0)
stream_component_close(is, is->video_stream);
if (is->subtitle_stream >= 0)
stream_component_close(is, is->subtitle_stream);
if (is->ic) {
av_close_input_file(is->ic);
is->ic = NULL; /* safety */
}
url_set_interrupt_cb(NULL);
if (ret != 0) {
SDL_Event event;
event.type = FF_QUIT_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);
}
return 0;
}
4、下面再来分析视频解码线程（函数为 ffplay.c / stream_component_open()）
下面是解码线程
[csharp] view
plaincopyprint?
static int stream_component_open(VideoState *is, int stream_index)
{
AVFormatContext *ic = is->ic;
AVCodecContext *enc;
AVCodec *codec;
<strong>SDL_AudioSpec wanted_spec, spec;</strong>
if (stream_index < 0 || stream_index >= ic->nb_streams)
return -1;
enc = ic->streams[stream_index]->codec;
/* prepare audio output */
if (enc->codec_type == CODEC_TYPE_AUDIO) { //如果为音频解码，需要初始化参数
if (enc->channels > 0) {
enc->request_channels = FFMIN(2, enc->channels);
} else {
enc->request_channels = 2;
}
}
codec = avcodec_find_decoder(enc->codec_id); //根据id找到具体的解码器
enc->debug_mv = debug_mv;
enc->debug = debug;
enc->workaround_bugs = workaround_bugs;
enc->lowres = lowres;
if(lowres) enc->flags |= CODEC_FLAG_EMU_EDGE;
enc->idct_algo= idct;
if(fast) enc->flags2 |= CODEC_FLAG2_FAST;
enc->skip_frame= skip_frame;
enc->skip_idct= skip_idct;
enc->skip_loop_filter= skip_loop_filter;
enc->error_recognition= error_recognition;
enc->error_concealment= error_concealment;
set_context_opts(enc, avctx_opts[enc->codec_type], 0); //set decode option
if (!codec ||
avcodec_open(enc, codec) < 0) //open decode
return -1;
/* prepare audio output */
if (enc->codec_type == CODEC_TYPE_AUDIO) {
wanted_spec.freq = enc->sample_rate;
wanted_spec.format = AUDIO_S16SYS;
wanted_spec.channels = enc->channels;
wanted_spec.silence = 0;
wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;
wanted_spec.callback = <strong><span style="color:#ff0000;">sdl_audio_callback</span></strong>; //此处初始化了一个音频解码线程(线程是在SDL中实现的，此接口是对用户提供了一个回调函数接口)
wanted_spec.userdata = is;
if (SDL_OpenAudio(&wanted_spec, &spec) < 0) {
fprintf(stderr, "SDL_OpenAudio: %s\n", SDL_GetError());
return -1;
}
is->audio_hw_buf_size = spec.size;
is->audio_src_fmt= SAMPLE_FMT_S16;
}
if(thread_count>1)
avcodec_thread_init(enc, thread_count); //解码线程初始化
enc->thread_count= thread_count;
ic->streams[stream_index]->discard = AVDISCARD_DEFAULT;
switch(enc->codec_type) {
case CODEC_TYPE_AUDIO:
is->audio_stream = stream_index;
is->audio_st = ic->streams[stream_index];
is->audio_buf_size = 0;
is->audio_buf_index = 0;
/* init averaging filter */
is->audio_diff_avg_coef = exp(log(0.01) / AUDIO_DIFF_AVG_NB);
is->audio_diff_avg_count = 0;
/* since we do not have a precise anough audio fifo fullness,
we correct audio sync only if larger than this threshold */
is->audio_diff_threshold = 2.0 * SDL_AUDIO_BUFFER_SIZE / enc->sample_rate;
memset(&is->audio_pkt, 0, sizeof(is->audio_pkt));
packet_queue_init(&is->audioq);
SDL_PauseAudio(0);
break;
case CODEC_TYPE_VIDEO:
is->video_stream = stream_index;
is->video_st = ic->streams[stream_index];
is->frame_last_delay = 40e-3;
is->frame_timer = (double)av_gettime() / 1000000.0;
is->video_current_pts_time = av_gettime();
packet_queue_init(&is->videoq);
is->video_tid = SDL_CreateThread(video_thread, is); //如果为视频，则创建一个视频处理线程
break;
case CODEC_TYPE_SUBTITLE:
is->subtitle_stream = stream_index;
is->subtitle_st = ic->streams[stream_index];
packet_queue_init(&is->subtitleq);
is->subtitle_tid = SDL_CreateThread(subtitle_thread, is);
break;
default:
break;
}
return 0;
}
5、接着分析video_thread线程:
[csharp] view
plaincopyprint?
static int video_thread(void *arg)
{
VideoState *is = arg;
AVPacket pkt1, *pkt = &pkt1;
int len1, got_picture;
AVFrame *frame= avcodec_alloc_frame();
double pts;
for(;;) {
while (is->paused && !is->videoq.abort_request) {
SDL_Delay(10);
}
if (packet_queue_get(&is->videoq, pkt, 1) < 0) //从队列获取一帧数据
break;
if(pkt->data == flush_pkt.data){ //如果当前包的数据等于清空包的数据，则刷新解码器的缓冲
avcodec_flush_buffers(is->video_st->codec);
continue;
}
/* NOTE: ipts is the PTS of the _first_ picture beginning in
this packet, if any */
is->video_st->codec->reordered_opaque= pkt->pts;
len1 = avcodec_decode_video(is->video_st->codec, //解码视频
frame, &got_picture,
pkt->data, pkt->size);
if( (decoder_reorder_pts || pkt->dts == AV_NOPTS_VALUE) //解码or播放的时间 dts、pts
&& frame->reordered_opaque != AV_NOPTS_VALUE)
pts= frame->reordered_opaque;
else if(pkt->dts != AV_NOPTS_VALUE)
pts= pkt->dts;
else
pts= 0;
pts *= av_q2d(is->video_st->time_base);
// if (len1 < 0)
// break;
if (got_picture) {
if (output_picture2(is, frame, pts) < 0) //输出图像
goto the_end;
}
av_free_packet(pkt); //释放缓冲
if (step)
if (cur_stream)
stream_pause(cur_stream);
}
the_end:
av_free(frame);
return 0;
}
6、最后分析一下main中的event_loop()
[csharp] view
plaincopyprint?
/* handle an event sent by the GUI */
static void event_loop(void)
{
SDL_Event event;
double incr, pos, frac;
for(;;) {
SDL_WaitEvent(&event);
switch(event.type) {
case SDL_KEYDOWN: //如果为按键事件
switch(event.key.keysym.sym) {
case SDLK_ESCAPE:
case SDLK_q: //如果按下 Q 则退出
do_exit();
break;
case SDLK_f: //如果按下 F 则全屏
toggle_full_screen();
break;
case SDLK_p:
case SDLK_SPACE: //如果按下SPACE 则暂停
toggle_pause();
break;
case SDLK_s: //S: Step to next frame
step_to_next_frame();
break;
case SDLK_a:
if (cur_stream)
stream_cycle_channel(cur_stream, CODEC_TYPE_AUDIO);
break;
case SDLK_v:
if (cur_stream)
stream_cycle_channel(cur_stream, CODEC_TYPE_VIDEO);
break;
case SDLK_t:
if (cur_stream)
stream_cycle_channel(cur_stream, CODEC_TYPE_SUBTITLE);
break;
case SDLK_w:
toggle_audio_display();
break;
case SDLK_LEFT:
incr = -10.0;
goto do_seek;
case SDLK_RIGHT:
incr = 10.0;
goto do_seek;
case SDLK_UP:
incr = 60.0;
goto do_seek;
case SDLK_DOWN:
incr = -60.0;
do_seek:
if (cur_stream) {
if (seek_by_bytes) {
pos = url_ftell(cur_stream->ic->pb);
if (cur_stream->ic->bit_rate)
incr *= cur_stream->ic->bit_rate / 60.0;
else
incr *= 180000.0;
pos += incr;
stream_seek(cur_stream, pos, incr);
} else {
pos = get_master_clock(cur_stream);
pos += incr;
stream_seek(cur_stream, (int64_t)(pos * AV_TIME_BASE), incr);
}
}
break;
default:
break;
}
break;
case SDL_MOUSEBUTTONDOWN:
if (cur_stream) {
int ns, hh, mm, ss;
int tns, thh, tmm, tss;
tns = cur_stream->ic->duration/1000000LL;
thh = tns/3600;
tmm = (tns%3600)/60;
tss = (tns%60);
frac = (double)event.button.x/(double)cur_stream->width;
ns = frac*tns;
hh = ns/3600;
mm = (ns%3600)/60;
ss = (ns%60);
fprintf(stderr, "Seek to %2.0f%% (%2d:%02d:%02d) of total duration (%2d:%02d:%02d) \n", frac*100,
hh, mm, ss, thh, tmm, tss);
stream_seek(cur_stream, (int64_t)(cur_stream->ic->start_time+frac*cur_stream->ic->duration), 0);
}
break;
case SDL_VIDEORESIZE:
if (cur_stream) {
screen = SDL_SetVideoMode(event.resize.w, event.resize.h, 0,
SDL_HWSURFACE|SDL_RESIZABLE|SDL_ASYNCBLIT|SDL_HWACCEL);
screen_width = cur_stream->width = event.resize.w;
screen_height= cur_stream->height= event.resize.h;
}
break;
case SDL_QUIT:
case FF_QUIT_EVENT:
do_exit();
break;
case FF_ALLOC_EVENT:
video_open(event.user.data1);
alloc_picture(event.user.data1);
break;
case FF_REFRESH_EVENT: //若是刷新时间，则显示图像
video_refresh_timer(event.user.data1);
break;
default:
break;
}
}
1、main()开始：
分别注册编解码器，复用以及解复用器
[cpp] view
plaincopyprint?
avcodec_register_all(); //register codec
avdevice_register_all();
av_register_all(); //register demux and mux
接着就是一些分配内存空间的代码
代码 略
[csharp] view
plaincopyprint?
parse_options(argc, argv, options, opt_input_file); //分析是否带有选项？
flags = SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER; //设置SDL的参数，我们选择了显示图像声音，并注册了一个定时器
SDL_Init (flags) <span style="white-space:pre"> </span>//初始化SDL
SDL_EventState(SDL_ACTIVEEVENT, SDL_IGNORE); //设置SDL的响应事件
SDL_EventState(SDL_MOUSEMOTION, SDL_IGNORE);
SDL_EventState(SDL_SYSWMEVENT, SDL_IGNORE);
SDL_EventState(SDL_USEREVENT, SDL_IGNORE);
av_init_packet(&flush_pkt); //初始化一个AVPacket
这个是重点：
[csharp] view
plaincopyprint?
cur_stream = stream_open(input_filename, file_iformat); //打开一个流，可以是file,tcp,rtp,udp,http等
2、具体分析stream_open()函数：
首先初始化了显示视频要的互斥锁，条件变量
[csharp] view
plaincopyprint?
is->pictq_mutex = SDL_CreateMutex();
is->pictq_cond = SDL_CreateCond();
is->subpq_mutex = SDL_CreateMutex();
is->subpq_cond = SDL_CreateCond();
/* add the refresh timer to draw the picture */
schedule_refresh(is, 40);
is->parse_tid = SDL_CreateThread(decode_thread, is); //创建解码线程
stream_open()函数调用结束。
3、接着分析decode_thread线程：
开始会初始化VideoState的部分参数
[csharp] view
plaincopyprint?
static int decode_thread(void *arg)
{
VideoState *is = arg;
AVFormatContext *ic;
int err, i, ret, video_index, audio_index, subtitle_index;
AVPacket pkt1, *pkt = &pkt1;
AVFormatParameters params, *ap = ¶ms;
video_index = -1;
audio_index = -1;
subtitle_index = -1;
is->video_stream = -1;
is->audio_stream = -1;
is->subtitle_stream = -1;
global_video_state = is;
url_set_interrupt_cb(decode_interrupt_cb);
memset(ap, 0, sizeof(*ap));
ap->width = frame_width;
ap->height= frame_height;
ap->time_base= (AVRational){1, 25};
ap->pix_fmt = frame_pix_fmt;
err = av_open_input_file(&ic, is->filename, is->iformat, 0, ap); //要求打开文件或流
if (err < 0) {
print_error(is->filename, err);
ret = -1;
goto fail;
}
is->ic = ic;
if(genpts)
ic->flags |= AVFMT_FLAG_GENPTS;
err = av_find_stream_info(ic); //从文件中找到媒体即填充AVFormatContext结构体
if (err < 0) {
fprintf(stderr, "%s: could not find codec parameters\n", is->filename);
ret = -1;
goto fail;
}
if(ic->pb)
ic->pb->eof_reached= 0; //FIXME hack, ffplay maybe should not use url_feof() to test for the end
/* if seeking requested, we execute it */
if (start_time != AV_NOPTS_VALUE) {
int64_t timestamp;
timestamp = start_time;
/* add the stream start time */
if (ic->start_time != AV_NOPTS_VALUE)
timestamp += ic->start_time;
ret = av_seek_frame(ic, -1, timestamp, AVSEEK_FLAG_BACKWARD);
if (ret < 0) {
fprintf(stderr, "%s: could not seek to position %0.3f\n",
is->filename, (double)timestamp / AV_TIME_BASE);
}
}
for(i = 0; i < ic->nb_streams; i++) { //从流中探测是否有音频流和视频流,字幕流，并将找到的流ID赋值给video
AVCodecContext *enc = ic->streams[i]->codec;//_index,探测完所有的流后，退出
ic->streams[i]->discard = AVDISCARD_ALL;
switch(enc->codec_type) {
case CODEC_TYPE_AUDIO:
if (wanted_audio_stream-- >= 0 && !audio_disable)
audio_index = i; //found audio stream
break;
case CODEC_TYPE_VIDEO:
if (wanted_video_stream-- >= 0 && !video_disable)
video_index = i; //founf video stream
break;
case CODEC_TYPE_SUBTITLE:
if (wanted_subtitle_stream-- >= 0 && !video_disable)
subtitle_index = i; //found subtile stream
break;
default:
break;
}
}
if (show_status) {
dump_format(ic, 0, is->filename, 0);//
dump_stream_info(ic);
}
/* open the streams */
if (audio_index >= 0) {
stream_component_open(is, audio_index); //此函数里，会新建一个解码线程，用于音频解码
}
if (video_index >= 0) {
stream_component_open(is, video_index); //此函数里，会新建一个解码线程，用于视频解码
} else {
if (!display_disable)
is->show_audio = 1;
}
if (subtitle_index >= 0) {
stream_component_open(is, subtitle_index);
}
if (is->video_stream < 0 && is->audio_stream < 0) {
fprintf(stderr, "%s: could not open codecs\n", is->filename);
ret = -1;
goto fail;
}
for(;;) {
if (is->abort_request)
break;
if (is->paused != is->last_paused) {
is->last_paused = is->paused;
if (is->paused)
av_read_pause(ic);
else
av_read_play(ic);
}
#if CONFIG_RTSP_DEMUXER
if (is->paused && !strcmp(ic->iformat->name, "rtsp")) {
/* wait 10 ms to avoid trying to get another packet */
/* XXX: horrible */
SDL_Delay(10);
continue;
}
#endif
if (is->seek_req) {
int stream_index= -1;
int64_t seek_target= is->seek_pos;
if (is-> video_stream >= 0) stream_index= is-> video_stream;
else if(is-> audio_stream >= 0) stream_index= is-> audio_stream;
else if(is->subtitle_stream >= 0) stream_index= is->subtitle_stream;
if(stream_index>=0){
seek_target= av_rescale_q(seek_target, AV_TIME_BASE_Q, ic->streams[stream_index]->time_base); //av_rescale_q(a,b,c)是用来把时间戳从一个时基调整到另外一个时基时候用的函数
}
ret = av_seek_frame(is->ic, stream_index, seek_target, is->seek_flags); //移动IC的指针(实现快进快退的功能)
if (ret < 0) {
fprintf(stderr, "%s: error while seeking\n", is->ic->filename);
}else{
if (is->audio_stream >= 0) {
packet_queue_flush(&is->audioq); //清空pkt队列缓冲区 ，这是因为is->seek_req==1,用户要实现视频片段的跳转。在跳转到一个新的片段时，之前的缓冲区需要清空
packet_queue_put(&is->audioq, &flush_pkt); //队列已经被清空，需要将flush_pkt包(清空包)加入到队列，相当于一个链表的header(这样说不知道是不是正确)
}
if (is->subtitle_stream >= 0) {
packet_queue_flush(&is->subtitleq);
packet_queue_put(&is->subtitleq, &flush_pkt);
}
if (is->video_stream >= 0) {
packet_queue_flush(&is->videoq);
packet_queue_put(&is->videoq, &flush_pkt);
}
}
is->seek_req = 0;
}
/* if the queue are full, no need to read more */
if (is->audioq.size > MAX_AUDIOQ_SIZE ||
is->videoq.size > MAX_VIDEOQ_SIZE ||
is->subtitleq.size > MAX_SUBTITLEQ_SIZE) {
/* wait 10 ms */
SDL_Delay(10);
continue;
}
if(url_feof(ic->pb)) {
av_init_packet(pkt);
pkt->data=NULL;
pkt->size=0;
pkt->stream_index= is->video_stream;
packet_queue_put(&is->videoq, pkt);
continue;
}
ret = av_read_frame(ic, pkt); //读取一帧数据到pkt
if (ret < 0) {
if (ret != AVERROR_EOF && url_ferror(ic->pb) == 0) {
SDL_Delay(100); /* wait for user event */
continue;
} else
break;
}
if (pkt->stream_index == is->audio_stream) { //如果该帧为音频帧，则将该包加入到音频队列中
packet_queue_put(&is->audioq, pkt);
} else if (pkt->stream_index == is->video_stream) {
packet_queue_put(&is->videoq, pkt);
} else if (pkt->stream_index == is->subtitle_stream) {
packet_queue_put(&is->subtitleq, pkt);
} else {
av_free_packet(pkt); //如果不为以上的包，则释放该包。
}
}
/* wait until the end */
while (!is->abort_request) {
SDL_Delay(100);
}
ret = 0;
fail:
/* disable interrupting */
global_video_state = NULL;
/* close each stream */
if (is->audio_stream >= 0)
stream_component_close(is, is->audio_stream);
if (is->video_stream >= 0)
stream_component_close(is, is->video_stream);
if (is->subtitle_stream >= 0)
stream_component_close(is, is->subtitle_stream);
if (is->ic) {
av_close_input_file(is->ic);
is->ic = NULL; /* safety */
}
url_set_interrupt_cb(NULL);
if (ret != 0) {
SDL_Event event;
event.type = FF_QUIT_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);
}
return 0;
}
4、下面再来分析视频解码线程（函数为 ffplay.c / stream_component_open()）
下面是解码线程
[csharp] view
plaincopyprint?
static int stream_component_open(VideoState *is, int stream_index)
{
AVFormatContext *ic = is->ic;
AVCodecContext *enc;
AVCodec *codec;
<strong>SDL_AudioSpec wanted_spec, spec;</strong>
if (stream_index < 0 || stream_index >= ic->nb_streams)
return -1;
enc = ic->streams[stream_index]->codec;
/* prepare audio output */
if (enc->codec_type == CODEC_TYPE_AUDIO) { //如果为音频解码，需要初始化参数
if (enc->channels > 0) {
enc->request_channels = FFMIN(2, enc->channels);
} else {
enc->request_channels = 2;
}
}
codec = avcodec_find_decoder(enc->codec_id); //根据id找到具体的解码器
enc->debug_mv = debug_mv;
enc->debug = debug;
enc->workaround_bugs = workaround_bugs;
enc->lowres = lowres;
if(lowres) enc->flags |= CODEC_FLAG_EMU_EDGE;
enc->idct_algo= idct;
if(fast) enc->flags2 |= CODEC_FLAG2_FAST;
enc->skip_frame= skip_frame;
enc->skip_idct= skip_idct;
enc->skip_loop_filter= skip_loop_filter;
enc->error_recognition= error_recognition;
enc->error_concealment= error_concealment;
set_context_opts(enc, avctx_opts[enc->codec_type], 0); //set decode option
if (!codec ||
avcodec_open(enc, codec) < 0) //open decode
return -1;
/* prepare audio output */
if (enc->codec_type == CODEC_TYPE_AUDIO) {
wanted_spec.freq = enc->sample_rate;
wanted_spec.format = AUDIO_S16SYS;
wanted_spec.channels = enc->channels;
wanted_spec.silence = 0;
wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;
wanted_spec.callback = <strong><span style="color:#ff0000;">sdl_audio_callback</span></strong>; //此处初始化了一个音频解码线程(线程是在SDL中实现的，此接口是对用户提供了一个回调函数接口)
wanted_spec.userdata = is;
if (SDL_OpenAudio(&wanted_spec, &spec) < 0) {
fprintf(stderr, "SDL_OpenAudio: %s\n", SDL_GetError());
return -1;
}
is->audio_hw_buf_size = spec.size;
is->audio_src_fmt= SAMPLE_FMT_S16;
}
if(thread_count>1)
avcodec_thread_init(enc, thread_count); //解码线程初始化
enc->thread_count= thread_count;
ic->streams[stream_index]->discard = AVDISCARD_DEFAULT;
switch(enc->codec_type) {
case CODEC_TYPE_AUDIO:
is->audio_stream = stream_index;
is->audio_st = ic->streams[stream_index];
is->audio_buf_size = 0;
is->audio_buf_index = 0;
/* init averaging filter */
is->audio_diff_avg_coef = exp(log(0.01) / AUDIO_DIFF_AVG_NB);
is->audio_diff_avg_count = 0;
/* since we do not have a precise anough audio fifo fullness,
we correct audio sync only if larger than this threshold */
is->audio_diff_threshold = 2.0 * SDL_AUDIO_BUFFER_SIZE / enc->sample_rate;
memset(&is->audio_pkt, 0, sizeof(is->audio_pkt));
packet_queue_init(&is->audioq);
SDL_PauseAudio(0);
break;
case CODEC_TYPE_VIDEO:
is->video_stream = stream_index;
is->video_st = ic->streams[stream_index];
is->frame_last_delay = 40e-3;
is->frame_timer = (double)av_gettime() / 1000000.0;
is->video_current_pts_time = av_gettime();
packet_queue_init(&is->videoq);
is->video_tid = SDL_CreateThread(video_thread, is); //如果为视频，则创建一个视频处理线程
break;
case CODEC_TYPE_SUBTITLE:
is->subtitle_stream = stream_index;
is->subtitle_st = ic->streams[stream_index];
packet_queue_init(&is->subtitleq);
is->subtitle_tid = SDL_CreateThread(subtitle_thread, is);
break;
default:
break;
}
return 0;
}
5、接着分析video_thread线程:
[csharp] view
plaincopyprint?
static int video_thread(void *arg)
{
VideoState *is = arg;
AVPacket pkt1, *pkt = &pkt1;
int len1, got_picture;
AVFrame *frame= avcodec_alloc_frame();
double pts;
for(;;) {
while (is->paused && !is->videoq.abort_request) {
SDL_Delay(10);
}
if (packet_queue_get(&is->videoq, pkt, 1) < 0) //从队列获取一帧数据
break;
if(pkt->data == flush_pkt.data){ //如果当前包的数据等于清空包的数据，则刷新解码器的缓冲
avcodec_flush_buffers(is->video_st->codec);
continue;
}
/* NOTE: ipts is the PTS of the _first_ picture beginning in
this packet, if any */
is->video_st->codec->reordered_opaque= pkt->pts;
len1 = avcodec_decode_video(is->video_st->codec, //解码视频
frame, &got_picture,
pkt->data, pkt->size);
if( (decoder_reorder_pts || pkt->dts == AV_NOPTS_VALUE) //解码or播放的时间 dts、pts
&& frame->reordered_opaque != AV_NOPTS_VALUE)
pts= frame->reordered_opaque;
else if(pkt->dts != AV_NOPTS_VALUE)
pts= pkt->dts;
else
pts= 0;
pts *= av_q2d(is->video_st->time_base);
// if (len1 < 0)
// break;
if (got_picture) {
if (output_picture2(is, frame, pts) < 0) //输出图像
goto the_end;
}
av_free_packet(pkt); //释放缓冲
if (step)
if (cur_stream)
stream_pause(cur_stream);
}
the_end:
av_free(frame);
return 0;
}
6、最后分析一下main中的event_loop()
[csharp] view
plaincopyprint?
/* handle an event sent by the GUI */
static void event_loop(void)
{
SDL_Event event;
double incr, pos, frac;
for(;;) {
SDL_WaitEvent(&event);
switch(event.type) {
case SDL_KEYDOWN: //如果为按键事件
switch(event.key.keysym.sym) {
case SDLK_ESCAPE:
case SDLK_q: //如果按下 Q 则退出
do_exit();
break;
case SDLK_f: //如果按下 F 则全屏
toggle_full_screen();
break;
case SDLK_p:
case SDLK_SPACE: //如果按下SPACE 则暂停
toggle_pause();
break;
case SDLK_s: //S: Step to next frame
step_to_next_frame();
break;
case SDLK_a:
if (cur_stream)
stream_cycle_channel(cur_stream, CODEC_TYPE_AUDIO);
break;
case SDLK_v:
if (cur_stream)
stream_cycle_channel(cur_stream, CODEC_TYPE_VIDEO);
break;
case SDLK_t:
if (cur_stream)
stream_cycle_channel(cur_stream, CODEC_TYPE_SUBTITLE);
break;
case SDLK_w:
toggle_audio_display();
break;
case SDLK_LEFT:
incr = -10.0;
goto do_seek;
case SDLK_RIGHT:
incr = 10.0;
goto do_seek;
case SDLK_UP:
incr = 60.0;
goto do_seek;
case SDLK_DOWN:
incr = -60.0;
do_seek:
if (cur_stream) {
if (seek_by_bytes) {
pos = url_ftell(cur_stream->ic->pb);
if (cur_stream->ic->bit_rate)
incr *= cur_stream->ic->bit_rate / 60.0;
else
incr *= 180000.0;
pos += incr;
stream_seek(cur_stream, pos, incr);
} else {
pos = get_master_clock(cur_stream);
pos += incr;
stream_seek(cur_stream, (int64_t)(pos * AV_TIME_BASE), incr);
}
}
break;
default:
break;
}
break;
case SDL_MOUSEBUTTONDOWN:
if (cur_stream) {
int ns, hh, mm, ss;
int tns, thh, tmm, tss;
tns = cur_stream->ic->duration/1000000LL;
thh = tns/3600;
tmm = (tns%3600)/60;
tss = (tns%60);
frac = (double)event.button.x/(double)cur_stream->width;
ns = frac*tns;
hh = ns/3600;
mm = (ns%3600)/60;
ss = (ns%60);
fprintf(stderr, "Seek to %2.0f%% (%2d:%02d:%02d) of total duration (%2d:%02d:%02d) \n", frac*100,
hh, mm, ss, thh, tmm, tss);
stream_seek(cur_stream, (int64_t)(cur_stream->ic->start_time+frac*cur_stream->ic->duration), 0);
}
break;
case SDL_VIDEORESIZE:
if (cur_stream) {
screen = SDL_SetVideoMode(event.resize.w, event.resize.h, 0,
SDL_HWSURFACE|SDL_RESIZABLE|SDL_ASYNCBLIT|SDL_HWACCEL);
screen_width = cur_stream->width = event.resize.w;
screen_height= cur_stream->height= event.resize.h;
}
break;
case SDL_QUIT:
case FF_QUIT_EVENT:
do_exit();
break;
case FF_ALLOC_EVENT:
video_open(event.user.data1);
alloc_picture(event.user.data1);
break;
case FF_REFRESH_EVENT: //若是刷新时间，则显示图像
video_refresh_timer(event.user.data1);
break;
default:
break;
}
}
内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理 
相关文章推荐
- ffplay程序运行流程分析
- ffplay程序运行流程分析
- ffplay程序运行流程分析
- mfc,示例 ctrlbars 程序运行流程分析
- WordCount程序运行流程分析
- Nematus（二）程序运行流程分析
- Play之Scala-Web项目运行流程-简单分析（3）
- C++运行时候库操作概述和整个程序运行流程
- Android:分析app、Process、Task之间的区别，以及获取最近运行的程序（近期任务）与正在运行的程序
- 程序运行 栈帧分析 以及 修改栈帧中数据以及函数地址
- (转)【Android游戏开发之十】（优化处理）详细剖析Android Traceview 效率检视工具！分析程序运行速度！并讲解两种创建SDcard方式！
- 详细剖析Android Traceview 效率检视工具！分析程序运行速度！并讲解两种创建SDcard方式！
- 如何利用JConsole观察分析JAVA程序的运行
- java笔记 chapter3 包装类，类型转换，程序的运行流程，面向对象的三大特征
- 如何利用 JConsole观察分析Java程序的运行，进行排错调优
- Wcf运行时执行流程分析
- ffplay_mfc流程分析-函数脑图
- Struts1程序的基本运行流程
- Android 当App内存不足或在后台运行时回收部分activity的流程分析。
- Uboot在ARM平台下运行流程分析