背景
最近調(diào)研做視頻秒開，使用B站開源的ijkplayer作為播放器厂捞。ijkplayer基于ffmpeg的播放器输玷。
ijkplayer使用
- 創(chuàng)建IjkMediaPlayer對象
- 通過setDataSource設(shè)置播放路徑
- 調(diào)用prepareAsync讓播放器開始工作
JNI_OnLoad
當(dāng)ijkplayer.so被加載時，會回調(diào)到IjkPlayer_jni.c中的JNI_OnLoad中靡馁，最主要調(diào)用ijkmp_global_init初始化
- 啊
ijkPlayer播放流程
- 在IjkMediaPlayer的構(gòu)造函數(shù)中欲鹏，
- 會調(diào)用
loadLibrariesOnce加載libijkffmpeg，ijksdl臭墨，ijkplayer這三個so - 調(diào)用
native_init打印了一行日志 - 初始化當(dāng)前線程Looper所使用的Handler
- 如果在有Looper的子線程初始化的話赔嚎，則會在該子線程進(jìn)行消息循環(huán)
- 如果沒有Looper的子線程，則使用主線程進(jìn)行消息循環(huán)
- 初始化一個Native層的IjkPlayer的引用
- 會調(diào)用
private void initPlayer(IjkLibLoader libLoader) {
loadLibrariesOnce(libLoader);
initNativeOnce();
Looper looper;
if ((looper = Looper.myLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else if ((looper = Looper.getMainLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else {
mEventHandler = null;
}
/*
* Native setup requires a weak reference to our object. It's easier to
* create it here than in C++.
*/
native_setup(new WeakReference<IjkMediaPlayer>(this));
}
- 調(diào)用
__setDataSource將視頻URL傳入Native層 - 調(diào)用
__prepareAsync告知Native層開始加載解碼 -
Ijkplayer_jni.c是IjkMediaPlayer對應(yīng)的C文件胧弛，其中setup完成以下事情：- 初始化Native的IjkMediaPlayer對象尤误，在
ijkmp_create函數(shù)中通過ffp_create初始化FFPlayer對象，并且將message_loop賦予該對象
- 初始化Native的IjkMediaPlayer對象尤误，在
static void IjkMediaPlayer_native_setup(JNIEnv *env, jobject thiz, jobject weak_this)
{
MPTRACE("%s\n", __func__);
// 創(chuàng)建Native層的IjkMediaPlayer對象结缚，并且將message_loop對象賦與mp->msg_loop
IjkMediaPlayer *mp = ijkmp_android_create(message_loop);
JNI_CHECK_GOTO(mp, env, "java/lang/OutOfMemoryError", "mpjni: native_setup: ijkmp_create() failed", LABEL_RETURN);
// 通過JNI將上步創(chuàng)建的IjkMediaPlayer對象的指針地址保存到Java層的mNativeMediaPlayer屬性中
// 并且釋放舊的IjkMediaPlayer
jni_set_media_player(env, thiz, mp);
// 重新生成IjkMediaPlayer的弱引用賦值mp->weak_thiz;
ijkmp_set_weak_thiz(mp, (*env)->NewGlobalRef(env, weak_this));
// 設(shè)置ffp的inject_opaque為上述弱引用
ijkmp_set_inject_opaque(mp, ijkmp_get_weak_thiz(mp));
ijkmp_set_ijkio_inject_opaque(mp, ijkmp_get_weak_thiz(mp));
ijkmp_android_set_mediacodec_select_callback(mp, mediacodec_select_callback, ijkmp_get_weak_thiz(mp));
LABEL_RETURN:
ijkmp_dec_ref_p(&mp);
}
-
setDataSource最終會調(diào)用到ijkmp_set_data_source_l- 將原來的
mp->data_source指針釋放 - 重新將url生成char *賦值給
mp->data_source - 將ijkmediaplayer對象的狀態(tài)修改成
MP_STATE_INITIALIZED
- 將原來的
static int ijkmp_set_data_source_l(IjkMediaPlayer *mp, const char *url)
{
...
freep((void**)&mp->data_source);
mp->data_source = strdup(url);
if (!mp->data_source)
return EIJK_OUT_OF_MEMORY;
ijkmp_change_state_l(mp, MP_STATE_INITIALIZED);
return 0;
}
-
prepareAsync最終也會調(diào)用到ijkmp_prepare_async_l中- 將ijkmediaplayer的狀態(tài)修改為
MP_STATE_ASYNC_PREPARING - 初始化消息隊列
&mp->ffplayer->msg_queue - 初始化消息處理線程损晤，線程處理function為
ijk_msg_loop - 調(diào)用
ffp_prepare_async_l調(diào)用ffmpeg中的方法開始prepare
- 將ijkmediaplayer的狀態(tài)修改為
static int ijkmp_prepare_async_l(IjkMediaPlayer *mp)
{
...
ijkmp_change_state_l(mp, MP_STATE_ASYNC_PREPARING);
// 向&mp->ffplayer->msg_queue中丟入一個FFP_MSG_FLUSH消息
// 最終目的只是初始化Native的MessageQueue
msg_queue_start(&mp->ffplayer->msg_queue);
// released in msg_loop
ijkmp_inc_ref(mp);
// 創(chuàng)建處理消息隊列的線程，
// 向Java層IjkMediaPlayer的postEventFromNative回調(diào)
// 該回調(diào)會回調(diào)到EventHandler中红竭，而隊列中只有FFP_MSG_FLUSH這個消息尤勋，這只是一個NOP的測試消息
mp->msg_thread = SDL_CreateThreadEx(&mp->_msg_thread, ijkmp_msg_loop, mp, "ff_msg_loop");
// msg_thread is detached inside msg_loop
// TODO: 9 release weak_thiz if pthread_create() failed;
int retval = ffp_prepare_async_l(mp->ffplayer, mp->data_source);
if (retval < 0) {
ijkmp_change_state_l(mp, MP_STATE_ERROR);
return retval;
}
return 0;
}
-
ffp_prepare_async_l中真正調(diào)用ffmpeg開始準(zhǔn)備播放- 判斷url協(xié)議是否為
rtmp或者rtsp喘落，如果是則取消timeout參數(shù) - 如果url長度大于1024，則加入
ijklongurl參數(shù) - 調(diào)用
stream_open打開視頻流最冰，使用FFPlayer播放
- 判斷url協(xié)議是否為
int ffp_prepare_async_l(FFPlayer *ffp, const char *file_name)
{
...
if (av_stristart(file_name, "rtmp", NULL) ||
av_stristart(file_name, "rtsp", NULL)) {
// There is total different meaning for 'timeout' option in rtmp
av_log(ffp, AV_LOG_WARNING, "remove 'timeout' option for rtmp.\n");
av_dict_set(&ffp->format_opts, "timeout", NULL, 0);
}
/* there is a length limit in avformat */
if (strlen(file_name) + 1 > 1024) {
av_log(ffp, AV_LOG_ERROR, "%s too long url\n", __func__);
if (avio_find_protocol_name("ijklongurl:")) {
av_dict_set(&ffp->format_opts, "ijklongurl-url", file_name, 0);
file_name = "ijklongurl:";
}
}
...
av_opt_set_dict(ffp, &ffp->player_opts);
if (!ffp->aout) {
ffp->aout = ffpipeline_open_audio_output(ffp->pipeline, ffp);
if (!ffp->aout)
return -1;
}
#if CONFIG_AVFILTER
if (ffp->vfilter0) {
GROW_ARRAY(ffp->vfilters_list, ffp->nb_vfilters);
ffp->vfilters_list[ffp->nb_vfilters - 1] = ffp->vfilter0;
}
#endif
// 打開視頻流
VideoState *is = stream_open(ffp, file_name, NULL);
if (!is) {
av_log(NULL, AV_LOG_WARNING, "ffp_prepare_async_l: stream_open failed OOM");
return EIJK_OUT_OF_MEMORY;
}
ffp->is = is;
ffp->input_filename = av_strdup(file_name);
return 0;
}
-
stream_open開始打開視頻流瘦棋，其中VideoState也就代表著視頻當(dāng)前的狀態(tài)，包括幀锌奴，數(shù)據(jù)兽狭，解碼器等等- 初始化幀隊列：
&is->pictq，&is->subpq鹿蜀，&is->sampq箕慧，Queue大小為16 - 初始化數(shù)據(jù)包隊列：
&is->videoq，&is->audioq茴恰，&is->subtitleq - 初始化時針：
&is->vidclk颠焦，&is->audclk，&is->extclk往枣，代表當(dāng)前視頻video伐庭，audio的時刻 - 創(chuàng)建視頻刷新的線程
is->video_refresh_tid - 創(chuàng)建視頻讀取線程
is->read_tid - 調(diào)用
decoder_init初始化視頻解碼器
- 初始化幀隊列：
static VideoState *stream_open(FFPlayer *ffp, const char *filename, AVInputFormat *iformat)
{
VideoState *is; // 視頻內(nèi)容以及狀態(tài)
...
/* start video display */
if (frame_queue_init(&is->pictq, &is->videoq, ffp->pictq_size, 1) < 0)
goto fail;
if (frame_queue_init(&is->subpq, &is->subtitleq, SUBPICTURE_QUEUE_SIZE, 0) < 0)
goto fail;
if (frame_queue_init(&is->sampq, &is->audioq, SAMPLE_QUEUE_SIZE, 1) < 0)
goto fail;
if (packet_queue_init(&is->videoq) < 0 ||
packet_queue_init(&is->audioq) < 0 ||
packet_queue_init(&is->subtitleq) < 0)
goto fail;
if (!(is->continue_read_thread = SDL_CreateCond())) {
av_log(NULL, AV_LOG_FATAL, "SDL_CreateCond(): %s\n", SDL_GetError());
goto fail;
}
if (!(is->video_accurate_seek_cond = SDL_CreateCond())) {
av_log(NULL, AV_LOG_FATAL, "SDL_CreateCond(): %s\n", SDL_GetError());
ffp->enable_accurate_seek = 0;
}
if (!(is->audio_accurate_seek_cond = SDL_CreateCond())) {
av_log(NULL, AV_LOG_FATAL, "SDL_CreateCond(): %s\n", SDL_GetError());
ffp->enable_accurate_seek = 0;
}
init_clock(&is->vidclk, &is->videoq.serial);
init_clock(&is->audclk, &is->audioq.serial);
init_clock(&is->extclk, &is->extclk.serial);
is->audio_clock_serial = -1;
...
is->video_refresh_tid = SDL_CreateThreadEx(&is->_video_refresh_tid, video_refresh_thread, ffp, "ff_vout");
if (!is->video_refresh_tid) {
av_freep(&ffp->is);
return NULL;
}
is->initialized_decoder = 0;
is->read_tid = SDL_CreateThreadEx(&is->_read_tid, read_thread, ffp, "ff_read");
if (!is->read_tid) {
av_log(NULL, AV_LOG_FATAL, "SDL_CreateThread(): %s\n", SDL_GetError());
goto fail;
}
if (ffp->async_init_decoder && !ffp->video_disable && ffp->video_mime_type && strlen(ffp->video_mime_type) > 0
&& ffp->mediacodec_default_name && strlen(ffp->mediacodec_default_name) > 0) {
if (ffp->mediacodec_all_videos || ffp->mediacodec_avc || ffp->mediacodec_hevc || ffp->mediacodec_mpeg2) {
decoder_init(&is->viddec, NULL, &is->videoq, is->continue_read_thread);
ffp->node_vdec = ffpipeline_init_video_decoder(ffp->pipeline, ffp);
}
}
is->initialized_decoder = 1;
return is;
fail:
is->initialized_decoder = 1;
is->abort_request = true;
if (is->video_refresh_tid)
SDL_WaitThread(is->video_refresh_tid, NULL);
stream_close(ffp);
return NULL;
}
FFMpeg模塊分布
encode/decode模塊
- 用于音視頻的編碼和解碼,存放在libavcodec子目錄中
muxer/demuxer模塊
- 用于音頻和視頻的合并與分離（也稱混合器模塊），存放在libavformat目錄中
內(nèi)存等常用模塊
- 存放于libavutil目錄中
總結(jié)
- IjkPlayer在Java層初始化主線程/當(dāng)前線程的EventHandler用于處理從Native層回調(diào)的消息
- 在Native層初始化IjkMediaPlayer對象
- 將
message_loop函數(shù)指針賦值分冈，以指定Native層的消息 - 通過
ffp_create創(chuàng)建FFPlayer對象 - 初始化IjkMediaPlayer中的Mutex圾另，以及
ref_count自增 - 創(chuàng)建SDK_Vout用于圖形渲染
- 根據(jù)平臺特性創(chuàng)建各平臺的IJKFF_Pipeline，PipeLine中包括了視頻解碼雕沉、音頻輸出等功能
- 將
- 將NativeMediaPlayer的指針地址賦值給Java層的
mNativeMediaPlayer - 當(dāng)調(diào)用
prepareAsync時集乔，Native層會從Java層獲取之前保存的mNativeMediaPlayer指針地址來獲取Native層的IjkMediaPlayer - 初始化
&mp->ffplayer->msg_queue - 啟動消息線程
&mp->_msg_thread以及消息循環(huán)函數(shù)ijkmp_msg_loop
參考資料
ijkplayer框架深入剖析
在線短視頻秒播優(yōu)化之視頻文件格式之MP4文件Moov box的位置
FFmpeg學(xué)習(xí)1：視頻解碼
MP4文件格式的解析，以及MP4文件的分割算法
ijkplayer整理筆記（三）——AVFormatContext類圖詳解類圖詳解
