Question

我正在努力理解使用ffmpeg的libavformat API将已经编码的x264帧放入视频容器文件中是什么以及不需要什么。

我当前的程序将获得x264帧-

while( x264_encoder_delayed_frames( h ) )
{
    printf("Writing delayed frame %u\n", delayed_frame_counter++);
    i_frame_size = x264_encoder_encode( h, &nal, &i_nal, NULL, &pic_out );
    if( i_frame_size < 0 ) {
            printf("Failed to encode a delayed x264 frame.\n");
            return ERROR;
        }
    else if( i_frame_size )
    {
        if( !fwrite(nal->p_payload, i_frame_size, 1, video_file_ptr) ) {
            printf("Failed to write a delayed x264 frame.\n");
            return ERROR;
        }
    }
}

如果我使用ffmpeg二进制文件的CLI，则可以使用以下命令将这些帧放入容器中：

ffmpeg -i "raw_frames.h264" -c:v copy -f mp4 "video.mp4"

我想使用libavformat API将此功能编码到我的程序中。我对需要调用每个ffmpeg函数的概念和顺序有些困惑。

到目前为止，我已经写过：

        mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
        printf("Guessed format\n");

        int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
        printf("Created context = %d\n", ret);
        printf("Format = %s\n", mAVFormatContext->oformat->name);

        mAVStream = avformat_new_stream(mAVFormatContext, 0);
        if (!mAVStream) {
            printf("Failed allocating output stream\n");
        } else {
            printf("Allocated stream.\n");
        }

        mAVCodecParameters = mAVStream->codecpar;
        if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
            mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
            mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
            printf("Invalid codec?\n");
        }

        if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
            ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
            if (ret < 0) {
              printf("Could not open output file '%s'", "gen_vid.mp4");
            }
          }

        ret = avformat_write_header(mAVFormatContext, NULL);
        if (ret < 0) {
          printf("Error occurred when opening output file\n");
        }

这将打印出来：

Guessed format
Created context = 0
Format = mp4
Allocated stream.
Invalid codec?
[mp4 @ 0x55ffcea2a2c0] Could not find tag for codec none in stream #0, codec not currently supported in container
Error occurred when opening output file

如何确保为我的视频正确设置了编解码器类型？接下来，我需要以某种方式指向我的mAVStream以使用我的x264帧-建议会很棒。

更新1： 因此，我尝试设置H264编解码器，以便可以使用编解码器的元数据。我现在似乎遇到了2个新问题。 1）它找不到设备，因此无法配置编码器。 2）我收到“未设置尺寸”。

mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
printf("Guessed format\n");

// MUST allocate the media file format context. 
int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
printf("Created context = %d\n", ret);
printf("Format = %s\n", mAVFormatContext->oformat->name);

// Even though we already have encoded the H264 frames using x264,
// we still need the codec's meta-data.
const AVCodec *mAVCodec;
mAVCodec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!mAVCodec) {
    fprintf(stderr, "Codec '%s' not found\n", "H264");
    exit(1);
}
mAVCodecContext = avcodec_alloc_context3(mAVCodec);
if (!mAVCodecContext) {
    fprintf(stderr, "Could not allocate video codec context\n");
    exit(1);
}
printf("Codec context allocated with defaults.\n");
/* put sample parameters */
mAVCodecContext->bit_rate = 400000;
mAVCodecContext->width = width;
mAVCodecContext->height = height;
mAVCodecContext->time_base = (AVRational){1, 30};
mAVCodecContext->framerate = (AVRational){30, 1};
mAVCodecContext->gop_size = 10;
mAVCodecContext->level = 31;
mAVCodecContext->max_b_frames = 1;
mAVCodecContext->pix_fmt = AV_PIX_FMT_NV12;

av_opt_set(mAVCodecContext->priv_data, "preset", "slow", 0);
printf("Set codec parameters.\n");

// Initialize the AVCodecContext to use the given AVCodec.
avcodec_open2(mAVCodecContext, mAVCodec, NULL);            

// Add a new stream to a media file. Must be called before
// calling avformat_write_header().
mAVStream = avformat_new_stream(mAVFormatContext, mAVCodec);
if (!mAVStream) {
    printf("Failed allocating output stream\n");
} else {
    printf("Allocated stream.\n");
}

// TODO How should codecpar be set?
mAVCodecParameters = mAVStream->codecpar;
if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
    mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
    mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
    printf("Invalid codec?\n");
}

if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
    ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
    if (ret < 0) {
      printf("Could not open output file '%s'", "gen_vid.mp4");
    }
  }
printf("Called avio_open()\n");

// MUST write a header.
ret = avformat_write_header(mAVFormatContext, NULL);
if (ret < 0) {
  printf("Error occurred when opening output file (writing header).\n");
}

现在我得到此输出-

Guessed format
Created context = 0
Format = mp4
Codec context allocated with defaults.
Set codec parameters.
[h264_v4l2m2m @ 0x556460344b40] Could not find a valid device
[h264_v4l2m2m @ 0x556460344b40] can't configure encoder
Allocated stream.
Invalid codec?
Called avio_open()
[mp4 @ 0x5564603442c0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
[mp4 @ 0x5564603442c0] dimensions not set
Error occurred when opening output file (writing header).

使用ffmpeg API将x264编码的帧放入mp4容器中

0 个答案: