[FFmpeg-devel] [PATCH] fixes in mpeg audio parsing

Michael Niedermayer michaelni
Thu Nov 13 23:51:56 CET 2008

On Thu, Nov 13, 2008 at 09:10:41PM +0200, Yoav Steinberg wrote:
> Michael Niedermayer wrote:
> > On Thu, Nov 13, 2008 at 06:59:17PM +0200, Yoav Steinberg wrote:
> > [...]
> >>> One certainly could have concatenated 2 mp3 files with a id3v1 ending in
> >>> the middle it would be nice if the parser & decoder would skip/ignore this
> >>> trash in the middle.
> >>> To me it seem that it shouldnt be too hard to make the parser skip
> >>> this, unless a valid id3v1 tag can also be a valid mp3 frame.
> >>>
> >> The current parser will, in most cases, skip id3v1 tags in the stream 
> >> which is good. But in one case the parser does actually think the tag is 
> >> part of a frame and does not skip it. This is when the tag was put 
> >> inside (overwriting) a frame's data. This isn't strictly valid, but it 
> >> turns out there are such files out there.
> > 
> > so, fix the parser
> I don't see how the parser can detect such a case. If the tag data is 
> inside the frame's data the parser will see a valid frame.

now i do not know if such case exists (maybe you could upload a sample?)
but assuming one exists then removing the last 128 byte will give you
a truncated frame. That does not appear more correct than leaving a
valid frame there.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Frequently ignored awnser#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
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