[FFmpeg-devel] [mp3] Skip APE tags when parsing mp3 packets.

[Michael Niedermayer]

On Mon, Jan 29, 2018 at 10:29:04PM -0300, James Almer wrote:
> On 1/29/2018 10:24 PM, Michael Niedermayer wrote:
> > On Mon, Jan 29, 2018 at 03:13:54PM -0800, Dale Curtis wrote:
> >> Otherwise the decoder will throw "Missing header" errors when the
> >> packets are sent for decoding.
> > 
> >>  mpegaudio_parser.c |    7 +++++++
> >>  1 file changed, 7 insertions(+)
> >> 2628fa8480b15237a528e94b1689da7321ce9440  skip-ape-tags.patch
> >> From 05f5e837862a958fb8791668ab3cdf8fc7766fe5 Mon Sep 17 00:00:00 2001
> >> From: Dale Curtis <dalecurtis at chromium.org>
> >> Date: Mon, 29 Jan 2018 15:10:26 -0800
> >> Subject: [PATCH] [mp3] Skip APE tags when parsing mp3 packets.
> >>
> >> Otherwise the decoder will throw "Missing header" errors when the
> >> packets are sent for decoding.
> >> ---
> >>  libavcodec/mpegaudio_parser.c | 7 +++++++
> >>  1 file changed, 7 insertions(+)
> >>
> >> diff --git a/libavcodec/mpegaudio_parser.c b/libavcodec/mpegaudio_parser.c
> >> index 8c39825792..244281b56f 100644
> >> --- a/libavcodec/mpegaudio_parser.c
> >> +++ b/libavcodec/mpegaudio_parser.c
> >> @@ -23,6 +23,7 @@
> >>  #include "parser.h"
> >>  #include "mpegaudiodecheader.h"
> >>  #include "libavutil/common.h"
> >> +#include "libavformat/apetag.h" // for APE tag.
> >>  #include "libavformat/id3v1.h" // for ID3v1_TAG_SIZE
> >>  
> >>  typedef struct MpegAudioParseContext {
> >> @@ -120,6 +121,12 @@ static int mpegaudio_parse(AVCodecParserContext *s1,
> >>          return next;
> >>      }
> >>  
> >> +    if (flush && buf_size >= APE_TAG_FOOTER_BYTES && memcmp(buf, APE_TAG_PREAMBLE, 8) == 0) {
> >> +        *poutbuf = NULL;
> >> +        *poutbuf_size = 0;
> >> +        return next;
> >> +    }
> > 
> > This doesnt feel right
> > 
> > Parsers should not discard data
> > 
> > a bistream filter could discard data, so could a demuxer if thats how the
> > format should be interpreted. Or the decoder could simply detect this case
> > and not print an error/warning
> 
> This patches duplicates existing code for id3v1 added by you in 89a420b71b5.
> I don't know if the rationale mentioned in the above commit is still
> valid today, and if it can be applied for apetag as intended by this
> patch, but there's at least a precedent for this.

yes, i have forgotten/missed this.

i ll apply the patch, as we already skip tags there ...
maybe this could be moved into a auto inserted bitstream filter or
something later. This was harder to do when the id3 skip code was added

[...]

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