[FFmpeg-devel] [PATCH] avformat/matroska: Parse generic encryption info from packets.

[Jacob Trimble]

On Mon, Aug 13, 2018 at 9:01 PM James Almer <jamrial at gmail.com> wrote:
>
> On 8/14/2018 12:50 AM, James Almer wrote:
> > On 7/12/2018 8:45 PM, Jacob Trimble wrote:
> >> I am currently seeing a problem with this when using Opus audio.  In
> >> read_frame_internal, it will try to parse the resulting packet.  For
> >> video, which uses subsample encryption, it is able to parse the
> >> headers; but for Opus, which uses full-sample encryption, it fails to
> >> parse the headers.  This causes the read_frame_internal to drop the
> >> packet.
> >>
> >> I have traced a workaround to opus_parse in opus_parser.c: instead of
> >> setting poutbuf to NULL, set it to the buffer and just pass the packet
> >> to the app to handle it.  The frame will be decrypted before passing
> >> to the decoder.  I can't just disable parsing in the demuxer because I
> >> want to parse the packets for clear content and when using subsample
> >> encryption.
> >>
> >> Does anyone have any other ideas to work around this?  Is there a way
> >> to allow parsing but ignore errors?
> > Try the attached diff to see if it fixes the issue (It makes the parser
> > not bother trying to assemble packets from what could be incomplete data
> > if the source is a demuxer that guarantees the propagation of complete
> > packets).
> >

Yep that fixed it, thanks.  I sent out a patch to implement that
(since other parsers do it, it seems like the correct thing to do).

In that case, this patch works well and is ready to review/merge.

> >
> > opus.diff
> >
> >
> > diff --git a/libavcodec/opus_parser.c b/libavcodec/opus_parser.c
> > index 28b0933900..e8d157356c 100644
> > --- a/libavcodec/opus_parser.c
> > +++ b/libavcodec/opus_parser.c
> > @@ -170,6 +170,9 @@ static int opus_parse(AVCodecParserContext *ctx, AVCodecContext *avctx,
> >      ParseContext *pc    = &s->pc;
> >      int next, header_len;
>
> Err, with the change below this should be initialized to 0 now. Sorry.
>
> >
> > +    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
> > +        next = buf_size;
> > +    } else {
> >      next = opus_find_frame_end(ctx, avctx, buf, buf_size, &header_len);
> >
> >      if (s->ts_framing && next != AVERROR_INVALIDDATA &&
> > @@ -184,6 +187,7 @@ static int opus_parse(AVCodecParserContext *ctx, AVCodecContext *avctx,
> >          *poutbuf_size = 0;
> >          return buf_size;
> >      }
> > +    }
> >
> >      *poutbuf      = buf + header_len;
> >      *poutbuf_size = buf_size - header_len;
> >
>
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