ffmpeg函数avcodec_receive_frame始终返回EAGAIN错误

问题描述

我正在使用ffmpeg在iOS上解码he-aac音频文件，该解码器是 libfdk_aac ，这是音频文件: https://cdn.perterpon.com/listen/test/bbc.mp4这是 av_dump_format 结果:

I’m using ffmpeg to decode he-aac audio file on iOS，which decoder is libfdk_aac，here is the audio file:https://cdn.perterpon.com/listen/test/bbc.mp4and here is the av_dump_format result:

Metadata:
    major_brand     : iso6
    minor_version   : 0
    compatible_brands: iso6dash
  Duration: N/A, bitrate: N/A
    Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, 2 channels (default)
    Metadata:
      handler_name    : USP Sound Handler

av_read_frame 和 avcodec_send_packet 返回0，但 avcodec_receive_frame 始终返回 AVERROR(EAGAIN)

av_read_frame and avcodec_send_packet return 0, but avcodec_receive_frame always return AVERROR(EAGAIN)

我尝试使用ffmpeg命令行工具: ffmpeg -i bbc.mp4 bbc.mp3 ，它成功了，并且mp3文件可以在iOS上播放.

I’v tried ffmpeg command line tool: ffmpeg -i bbc.mp4 bbc.mp3, it success, and the mp3 file is good to playback on iOS.

这是我的代码:

av_register_all();
AVFormatContext *avFormatContext = avformat_alloc_context();
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"bbc" ofType:@"mp4"];

int ret;
ret = avformat_open_input(&avFormatContext, [filePath UTF8String], NULL, NULL);
if (0 != ret) {
    NSLog(@"avformat_open_input failed: %d", ret);
}

ret = avformat_find_stream_info(avFormatContext, NULL);
if (0 != ret) {
    NSLog(@"avformat_find_stream_info: %d", ret);
}

// the libfdk_aac decoder
AVCodec *codec = avcodec_find_decoder_by_name("libfdk_aac");
AVCodecContext *codecContext = avcodec_alloc_context3(codec);

ret = avcodec_open2(codecContext, codec, NULL);
if (0 != ret) {
    NSLog(@"avcodec_open2 faild: %d", ret);
}

AVFrame *frame = av_frame_alloc();
AVPacket packet;
av_init_packet(&packet);

// start read data and decode data
while (true) {
    ret = av_read_frame(avFormatContext, &packet);
    if (0 != ret) {
        break;
    }
    ret = avcodec_send_packet(codecContext, &packet);
    if (ret != 0) {
        NSLog(@"send package with error: %d", ret);
        continue;
        break;
    }
    while (true) {
        // the ret below is always return -35, means AVERROR(EAGAIN)
        ret = avcodec_receive_frame(codecContext, frame);
        if (ret == AVERROR(EAGAIN)) {
            NSLog(@"avcodec_receive_frame with EAGAIN error: %d", ret);
            break;
        } else if (ret == AVERROR_EOF) {
            NSLog(@"end of file");
            break;
        }
    }
    if (ret == AVERROR(EAGAIN)) {
        continue;
    }
}

我尝试将 bbc.mp4 文件替换为 bbc.mp3 文件，并将解码器更改为: AVCodec * codec = avcodec_find_decoder(AV_CODEC_ID_MP3);，所有事情都运转良好.非常非常感谢你.

I'v tried replace bbc.mp4 file to bbc.mp3 file, and change the decoder to: AVCodec *codec = avcodec_find_decoder(AV_CODEC_ID_MP3);，all of the things working every good. Thank you very very very much.

推荐答案

当avcodec_receive_frame返回EAGAIN时，必须再次调用具有更多数据的avcodec_send_packet(或流末尾为空数据包)，然后才能再次调用avcodec_receive_frame.

When avcodec_receive_frame returns EAGAIN, you must call avcodec_send_packet with more data (or a null packet at the end of the stream) before calling avcodec_receive_frame again.

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