> Am 08.07.2018 um 10:58 schrieb Michael Niedermayer <mich...@niedermayer.cc>:
>
> Signierter PGP-Teil
> On Sat, Jul 07, 2018 at 10:29:11PM +0200, Karsten Otto wrote:
>> Check the MPEG version ID for the reserved bit pattern 01, and abort header
>> parsing in that case. This reduces the chance of misinterpreting arbitrary
>> data as a valid frame start, and prevents the resulting audio artifacts.
>> ---
>> libavcodec/mpegaudiodecheader.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/mpegaudiodecheader.c
>> b/libavcodec/mpegaudiodecheader.c
>> index 6cc79f18b5..23029f186a 100644
>> --- a/libavcodec/mpegaudiodecheader.c
>> +++ b/libavcodec/mpegaudiodecheader.c
>> @@ -46,10 +46,11 @@ int avpriv_mpegaudio_decode_header(MPADecodeHeader *s,
>> uint32_t header)
>> if (header & (1<<20)) {
>> s->lsf = (header & (1<<19)) ? 0 : 1;
>> mpeg25 = 0;
>> - } else {
>> + } else if (!(header & (1<<19))) {
>> s->lsf = 1;
>> mpeg25 = 1;
>> - }
>> + } else
>> + return -1; // reserved id
>
> This check (assuming it breaks no existing mp3) would fit better in
> ff_mpa_check_header()
>
I did not want to put it in ff_mpa_check_header(), since that is supposed to be
a
"fast header check for resync", emphasis *fast*. But if you think an extra
check is
acceptable, I can certainly put it there. Will send an update patch.
Re breaking existing mp3: I haven't checked the official ISO standard, but all
other
free reference material agrees bit pattern 01 is supposed to be reserved. I have
tested both with an mpeg 1 layer 3 (first branch) and mpeg2.5 layer 3 (second)
branch, with files I found on samples.ffmpeg.org. The patch also passes make
fate
(though I don't quite understand what that does, I assume it checks for such
things).
Cheers, Karsten
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
