iOS ijkplayer 音频数据的播放

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音频信息 SDL_AudioSpec 的产生read_thread ->stream_component_open(ffp, st_index[AVMEDIA_TYPE_AUDIO]);->/* prepare audio output */        if ((ret = audio_open(ffp, channel_layout, nb_channels, sample_rate, &is->audio_tgt)) < 0)->while (SDL_AoutOpenAudio(ffp->aout, &wanted_spec, &spec) < 0) ->static int aout_open_audio(SDL_Aout *aout, const SDL_AudioSpec *desired, SDL_AudioSpec *obtained)->opaque->aoutController = [[IJKSDLAudioQueueController alloc] initWithAudioSpec:desired];->SDL_CalculateAudioSpec(&_spec);->{    spec->size = SDL_AUDIO_BITSIZE(spec->format) / 8;    spec->size *= spec->channels;    spec->size *= spec->samples;//计算size大小}->aout_open_audio 里面-> if (obtained)        *obtained = opaque->aoutController.spec;//将上一步计算的spec 赋给  obtained ->static int aout_open_audio(SDL_Aout *aout, const SDL_AudioSpec *desired, SDL_AudioSpec *obtained)->while (SDL_AoutOpenAudio(ffp->aout, &wanted_spec, &spec) < 0) 既在这个函数执行完spec 就计算出来了。

static void IJKSDLAudioQueueOuptutCallback(void * inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer) {    @autoreleasepool {        JFSDLAudioQueueController* aqController = (__bridge JFSDLAudioQueueController *) inUserData;                if (!aqController) {            // do nothing;        } else if (aqController->_isPaused || aqController->_isStopped) {            memset(inBuffer->mAudioData, aqController.spec.silence, inBuffer->mAudioDataByteSize);        } else {                    (*aqController.spec.callback)(aqController.spec.userdata, inBuffer->mAudioData, inBuffer->mAudioDataByteSize);        }                AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL);    }}        (*aqController.spec.callback)(aqController.spec.userdata, inBuffer->mAudioData, inBuffer->mAudioDataByteSize);        }/* prepare a new audio buffer */static void sdl_audio_callback(void *opaque, Uint8 *stream, int len)

//此处选择输出是用AudioUnit还是用AudioQueue

/* * ijksdl_aout_ios_audiounit.m *#define SDL_IOS_AUDIO_MAX_CALLBACKS_PER_SEC 15struct SDL_Aout_Opaque {//    IJKSDLAudioQueueController *aoutController;        IJKSDLAudioUnitController  *aoutController;};static int aout_open_audio(SDL_Aout *aout, const SDL_AudioSpec *desired, SDL_AudioSpec *obtained){    assert(desired);    SDLTRACE("aout_open_audio()\n");    SDL_Aout_Opaque *opaque = aout->opaque;    //    opaque->aoutController = [[IJKSDLAudioQueueController alloc] initWithAudioSpec:desired];        opaque->aoutController = [[IJKSDLAudioUnitController alloc] initWithAudioSpec:desired];    if (!opaque->aoutController) {        ALOGE("aout_open_audio_n: failed to new AudioTrcak()\n");        return -1;    }        if (obtained)        *obtained = opaque->aoutController.spec;        return 0;}

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