quartz: Detect and skip id3v2 header in mpeg splitter

[Maarten Lankhorst]

Hi Chris,

2008/3/14, Chris Robinson <chris.kcat at gmail.com>:
> On Thursday 13 March 2008 09:01:53 pm Maarten Lankhorst wrote:
>  > If read from a file source, ID3 v2 tags might be incorrectly parsed by
>  > the head_check. This patch skips the whole tag altogether.
>
>
> I'm not sure this is completely correct. The main splitter function detects
>  the presense of an MP3 header at the start of a sample it's sending to set
>  the sample's sync point attribute. Since the ID3 tag is not a sync point,
>  this causes the first sample to not be set as a sync point, and it would be
>  unlikely that a following sample would, under normal circumstances, contain
>  an MP3 header at the start either. This could cause sensitive codecs to never
>  find a sync point.
In general the tag is not a sync point, but some data behind it
accidentally may be parsed as such. Even if it didn't, the tag is
generally a few 100 (or about 1000 in my case)  bytes in size. Reading
all those bytes individually and moving them all 4 times doesn't seem
really optimal. Skipping the amount of data that is set in the size
buffer causes it to immediately find the first mp3 header.

>  ACMWrapper wouldn't be affected as it doesn't handle sync points, but other
>  native codecs (which do work in Wine) could. Additionally, winemp3.acm may be
>  affected by the ID3 tag as it doesn't seem to have code to handle it either.
It doesn't affect sync points, everything in the id3 tag is garbage
and skipping it is a good thing (TM).

Cheers,
Maarten.