[Libav-user] [dnxhd] Internal error, put_bits buffer too small

[Jonathan Noble]

I've just searched for any instance of AVCodecContext->frame_size and it is
only read.

Here is a sample of how the AVCodecContext is setup

  // setup context
>   vcodec_ctx->codec_id = static_cast<AVCodecID>(video_params_.codec);
>   vcodec_ctx->codec_type = AVMEDIA_TYPE_VIDEO;
>   vcodec_ctx->width = video_params_.width;
>   vcodec_ctx->height = video_params_.height;
>   vcodec_ctx->sample_aspect_ratio = {1, 1};
>   vcodec_ctx->pix_fmt = vcodec->pix_fmts[0]; // maybe be breakable code
>   setupFrameRate(*vcodec_ctx, video_params_.frame_rate);
>   if (video_params_.compression_type == CompressionType::CBR) {
>     const auto brate = static_cast<int64_t>((video_params_.bitrate * 1E6)
> + 0.5);
>     vcodec_ctx->bit_rate = brate;
>     vcodec_ctx->rc_min_rate = brate;
>     vcodec_ctx->rc_max_rate = brate;
>   }
>   vcodec_ctx->time_base = av_inv_q(vcodec_ctx->framerate);
>   video_stream->time_base = vcodec_ctx->time_base;
>   vcodec_ctx->gop_size = video_params_.gop_length_;
>   vcodec_ctx->thread_count =
> static_cast<int>(std::thread::hardware_concurrency());
>
  // Do bare minimum before avcodec_open2
>   switch (vcodec_ctx->codec_id) {
>     case AV_CODEC_ID_H264:
>       setupH264Encoder(*vcodec_ctx, video_params_);
>       break;
>     case AV_CODEC_ID_MPEG2VIDEO:
>       setupMPEG2Encoder(*vcodec_ctx, video_params_);
>       break;
>     case AV_CODEC_ID_DNXHD:
>       setupDNXHDEncoder(*vcodec_ctx, video_params_);
>       break;
>     case AV_CODEC_ID_MPEG4:
>       setupMPEG4Encoder(*vcodec_ctx, video_params_);
>     default:
>       // Nothing defined for these codecs yet
>       break;
>   }
>
>   auto ret = avcodec_open2(vcodec_ctx, vcodec, &opts);
>   if (ret < 0) {
>     av_strerror(ret, err.data(), ERR_LEN);
>     qCritical() << "Could not open output video encoder." << err.data();
>     ed->export_error = tr("could not open output video encoder
> (%1)").arg(err.data());
>     return false;
>   }
>
>   if (fmt_ctx->oformat->flags & AVFMT_GLOBALHEADER) {
>     vcodec_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
>   }
>
>   vcodec_ctx->sample_aspect_ratio = {1, 1};
>   vcodec_ctx->max_b_frames = video_params_.b_frames_;
>
>   // copy video encoder parameters to output stream
>   ret = avcodec_parameters_from_context(video_stream->codecpar,
> vcodec_ctx);
>   if (ret < 0) {
>     av_strerror(ret, err.data(), ERR_LEN);
>     qCritical() << "Could not copy video encoder parameters to output
> stream, code=" << err.data();
>     ed->export_error = tr("could not copy video encoder parameters to
> output stream (%1)").arg(QString::number(ret));
>     return false;
>   }
>

 void ExportThread::setupDNXHDEncoder(AVCodecContext& ctx, const Params&
> video_params) const
> {
>   ctx.profile = FF_PROFILE_DNXHD;
>   // FIXME: DNXHDEncContext.pb needs setting up somehow
>
>   if (video_params.profile_.endsWith("x")) {
>     // dnxhdenc will deduce this as 10bits
>     if (!video_params.pix_fmts_.empty())
>     {
>       auto fmt = video_params.pix_fmts_.front();
>       switch (fmt)
>       {
>         case PixelFormat::YUV444:
>           ctx.pix_fmt = AV_PIX_FMT_YUV444P10;
>           break;
>         case PixelFormat::YUV422:
>           ctx.pix_fmt = AV_PIX_FMT_YUV422P10;
>           break;
>         case PixelFormat::YUV420:
>           // this may not be in any profile
>           ctx.pix_fmt = AV_PIX_FMT_YUV420P10;
>           break;
>       }
>     }
>   }
> }
>

On Thu, 3 Oct 2019 at 09:47, Paul B Mahol <onemda at gmail.com> wrote:

> On 10/3/19, Jonathan Noble <jonnobleuk at gmail.com> wrote:
> > It isn't reproduceable with ffmpeg. Am i in the wrong mailing-list?
>
> Perhaps you reset frame_size somehow?
>
> >
> > On Thu, 3 Oct 2019 at 07:47, Paul B Mahol <onemda at gmail.com> wrote:
> >
> >> Please provide input samples that allow to reproduce this issue with
> >> ffmpeg.
> >>
> >> On 10/2/19, Jonathan Noble <jonnobleuk at gmail.com> wrote:
> >> > Hi,
> >> >
> >> > I am trying to encode to dnxhd with libavcodec. The result is quite
> >> glitchy
> >> > with stuttering and anomalies on most frames.
> >> >
> >> > During encoding I see the following message almost continuously.
> >> >
> >> >> Internal error, put_bits buffer too small
> >> >
> >> > I have tried to understand what this buffer is, how it is set up and I
> >> > am
> >> > struggling. From what I can understand the puts_bit buffer is
> >> > DNXHDEncContext->m->pb which is initialised via init_put_bits() in
> >> > dnxhd_encode_thread().
> >> >
> >> > The 2 arguments used in init_put_bits() are
> DNXHDEncContext->slice_offs
> >> and
> >> > DNXHDEncContext->slice_size. These 2 are configured in
> >> > dnxhd_setup_thread_slices() with 2 variables MpegEncContext->mb_width
> >> > and
> >> > MpegEncContext->mb_bits.
> >> >
> >> > If my understanding is correct the 2 aforementioned variables in
> >> > MpegEncContext are the variables I need to set. However, I have no
> idea
> >> > what they mean or how they are accessed outside of
> >> > AVCodecContext->priv_data.
> >> >
> >> > Is my understanding correct? How does one setup the puts_bit buffer
> >> > correctly for a dnxhd encode?
> >> >
> >> > Kind regards
> >> >
> >> > Jon Noble
> >> >
> >> _______________________________________________
> >> Libav-user mailing list
> >> Libav-user at ffmpeg.org
> >> https://ffmpeg.org/mailman/listinfo/libav-user
> >>
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> >> libav-user-request at ffmpeg.org with subject "unsubscribe".
> >
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