libavformat/libavcodec提供了无效的容器头 [英] libavformat/libavcodec providing invalid container header
问题描述
我正在使用libavcodec将流编码为h264，并使用libavformat将其存储在mp4中.产生的容器具有无效的标头，可以在VLC中播放，但不能在任何其他播放器上播放.
I'm using libavcodec to encode a stream to h264 and libavformat to store it in an mp4. The resulting container has an invalid header that can be played in VLC, but not any other player.
我发现使用mp4容器和"mpeg4"编解码器会生成有效的mp4文件，但是使用libx265(HEVC)或libx264编解码器会生成无效的mp4.
I've found that using the mp4 container and the "mpeg4" codec produces a valid mp4 file, but using libx265 (HEVC) or the libx264 codec produces invalid mp4s.
我可以使用 ffmpeg -i invalid.mp4 -vcodec复制valid.mp4 ，我得到一个几乎完全相同大小的文件，但是在一个有效的容器中.
I can use ffmpeg -i invalid.mp4 -vcodec copy valid.mp4 and I get a file of almost the exact same size, but in a valid container.
以下是这些文件的示例:损坏的文件和已拒绝文件 [使用右上角的下载链接进行检查]
Examples of these files are here: Broken file and Repaied file [use the download links in the upper right to examine]
我使用了十六进制编辑器来查看两个文件的标题之间的差异，无效的文件比有效文件小1个字节.
I used a hex editor to see the differences in the headers of the two files and the invalid one is 1 byte smaller than the valid one.
我用来打开容器和编解码器并编写标题的代码在这里:
The code I'm using to open the container and codec and to write the header is here:
AVOutputFormat *container_format;
AVFormatContext *container_format_context;
AVStream *video_stream;
int ret;
/* allocate the output media context */
avformat_alloc_output_context2(&container_format_context, NULL, NULL, out_file);
if (!container_format_context) {
log(INFO, "Unable to determine container format from filename, exiting\n");
exit(1);
}
else {
log(INFO, "Using container %s\n", container_format_context->oformat->name);
}
if (!container_format_context) {
log(ERROR, "Could not build container format context. Encoding failed.");
exit(1);
}
container_format = container_format_context->oformat;
/* Pull codec based on name */
AVCodec* codec = avcodec_find_encoder_by_name(codec_name);
if (codec == NULL) {
log(ERROR, "Failed to locate codec \"%s\".",
codec_name);
exit(1);
}
/* create stream */
video_stream = NULL;
video_stream = avformat_new_stream(container_format_context, codec);
if (!video_stream) {
log(ERROR, "Could not allocate encoder stream. Cannot continue.\n");
exit(1);
}
video_stream->id = container_format_context->nb_streams - 1;
video_stream->time_base = video_stream->codec->time_base = (AVRational) { 1, 25};
av_dump_format(container_format_context, 0, out_file, 1);
/* Retrieve encoding context */
AVCodecContext* avcodec_context = video_stream->codec;
if (avcodec_context == NULL) {
log(ERROR, "Failed to allocate context for "
"codec \"%s\".", codec_name);
exit(1);
}
/* Init context with encoding parameters */
avcodec_context->bit_rate = bitrate;
avcodec_context->width = width;
avcodec_context->height = height;
avcodec_context->gop_size = 10;
avcodec_context->max_b_frames = 1;
avcodec_context->qmax = 31;
avcodec_context->qmin = 2;
avcodec_context->pix_fmt = AV_PIX_FMT_YUV420P;
av_dump_format(container_format_context, 0, out_file, 1);
/* Open codec for use */
if (avcodec_open2(avcodec_context, codec, NULL) < 0) {
log(ERROR, "Failed to open codec \"%s\".", codec_name);
exit(1);
}
/* Allocate corresponding frame */
AVFrame* frame = av_frame_alloc();
if (frame == NULL) {
exit(1);
}
/* Copy necessary data for frame from avcodec_context */
frame->format = avcodec_context->pix_fmt;
frame->width = avcodec_context->width;
frame->height = avcodec_context->height;
/* Allocate actual backing data for frame */
if (av_image_alloc(frame->data, frame->linesize, frame->width,
frame->height, frame->format, 32) < 0) {
exit(1);
}
/* open the output file, if the container needs it */
if (!(container_format->flags & AVFMT_NOFILE)) {
ret = avio_open(&container_format_context->pb, out_file, AVIO_FLAG_WRITE);
if (ret < 0) {
log(ERROR, "Error occurred while opening output file: %s\n",
av_err2str(ret));
exit(1);
}
}
/* write the stream header, if needed */
ret = avformat_write_header(container_format_context, NULL);
if (ret < 0) {
log(ERROR, "Error occurred while writing output file header: %s\n",
av_err2str(ret));
}
编码帧的代码在这里:
/* Init video packet */
AVPacket packet;
av_init_packet(&packet);
/* Request that encoder allocate data for packet */
packet.data = NULL;
packet.size = 0;
/* Write frame to video */
int got_data;
if (avcodec_encode_video2(avcontext, &packet, frame, &got_data) < 0) {
log(WARNING, "Error encoding frame #%" PRId64,
video_struct->next_pts);
return -1;
}
/* Write corresponding data to file */
if (got_data) {
if (packet.pts != AV_NOPTS_VALUE) {
packet.pts = av_rescale_q(packet.pts, video_struct->output_stream->codec->time_base, video_struct->output_stream->time_base);
}
if (packet.dts != AV_NOPTS_VALUE) {
packet.dts = av_rescale_q(packet.dts, video_struct->output_stream->codec->time_base, video_struct->output_stream->time_base);
}
write_packet(video_struct, &packet, packet.size);
av_packet_unref(&packet);
}
以及将数据包写入视频流的代码:
And the code to write the packet to the video stream:
static int write_packet(video_struct* video, void* data, int size) {
int ret;
/* use AVStream is not null, otherwise write to output fd */
AVPacket *pkt = (AVPacket*) data;
pkt->stream_index = video->output_stream->index;
ret = av_interleaved_write_frame(video->container_format_context, pkt);
if (ret != 0) {
return -1;
}
/* Data was written successfully */
return ret;
}
推荐答案
解决了此问题.问题是如果容器需要的话，我没有为容器分配全局头.在为 avcodec_context 分配高度，宽度，比特率等属性时，我添加了
Solved this issue. The problem was that I wasn't assigning global headers to the container if the container required it. While assigning properties like height, width, bit rate and so forth to the avcodec_context, I added
if (container_format_context->oformat->flags & AVFMT_GLOBALHEADER) {
avcodec_context->flags |= CODEC_FLAG_GLOBAL_HEADER;
}
这似乎已解决了该问题.
which seems to have fixed the issue.
这篇关于libavformat/libavcodec提供了无效的容器头的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
