Question

我正在尝试使用ffmpeg-sdl2和emscripten编写sdl2视频播放器。我有一个解码数据包并将缓冲区添加到SDL_QueuAudio的函数。我在js中这样称呼queueAudioFrame()：

setInterval(function () {
        this._queueAudioFrame();
    }, 1);

这是实现的C端：

int DecodeAudioPacket(AVPacket packet, AVCodecContext* ctx, uint8_t* audioBuf, int bufSize)
{
  AVFrame* frame = NULL;
  uint8_t converted_data[(192000 * 3) / 2];
  uint8_t* converted;

  int len1, len2, dataSize = 0;

  if (!frame)
  {
    frame = av_frame_alloc();
    converted = &converted_data[0];
  }

  int gotFrame = 0;
  len1 = avcodec_decode_audio4(ctx, frame, &gotFrame, &packet);

  if (len1 < 0)
  {
    return 0;
  }
  if (gotFrame)
  {

    dataSize = av_samples_get_buffer_size(NULL, ctx->channels, frame->nb_samples, ctx->sample_fmt, 1);
    int outSize = av_samples_get_buffer_size(NULL, ctx->channels, frame->nb_samples, AV_SAMPLE_FMT_FLT, 1);
    len2 = swr_convert(swrCtx, &converted, frame->nb_samples, (const uint8_t**)&frame->data[0], frame->nb_samples);
    memcpy(audioBuf, converted_data, outSize);
    dataSize = outSize;
  }

  if (packet.data)
  {
    av_free_packet(&packet);
  }

  if (dataSize <= 0) {
    /* No data yet, get more frames */
    return 0;
  }

  /* We have data, return it and come back for more later */
  return dataSize;
}

void EMSCRIPTEN_KEEPALIVE queueAudioFrame()
{
  if (av_read_frame(audiopFormatCtx, &audiopacket) >= 0) 
  {
    if (audiopacket.stream_index != videoStream)
    {
        uint8_t audioBuf[(192000 * 3) / 2];

        int decodeSize = DecodeAudioPacket(audiopacket, audioCtx, audioBuf, sizeof(audioBuf));
        queued = SDL_GetQueuedAudioSize(1);
        printf("Decoded bytes from frame: %d & Device has %u bytes queued. \n", decodeSize, queued);
        SDL_QueueAudio(1, audioBuf, decodeSize);
    }
  }
}

我从法典和wantedSpec.freq = audioCtx->sample_rate;获得了采样率。问题是音频播放速度太快，无论我设置为wantSpec.freq还是wantSpec.samples速度的值不变。是什么原因造成的？

为什么更改频率不会影响sdl音频的播放速度（脚本）？

0 个答案: