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

[Yoav Steinberg]

Michael Niedermayer wrote:
> On Wed, Nov 12, 2008 at 07:02:55PM +0200, Yoav Steinberg wrote:
>> Hi,
>> Attached are patches witch make some improvements for mp3 parsing.
>> skip_vbrtag_and_id3v1.patch:
> 
>> - When file contains ID3v1 tag at the end don't attempt to read it as part 
>> of a packet. In some cases there are mp3 files where the ID3v1 tag was 
>> stuck forcefully at the end of the file inside the last frame boundary. In 
>> those cases the patch eliminates attempts to parse/decode the ID3 tag.
>> - If we find a VBR tag at the beginning of the file don't attempt to parse 
>> it as a valid frame.
> 
> These are 2 seperate things which must be in seperate patches.

Here is a single patch for avoiding parsing of VBR tag information frames.

> 
>> @@ -439,8 +446,14 @@
>>      }
>>  
>>      if(frames < 0)
>> +    {
>> +        url_fseek(s->pb, base, SEEK_SET);
>>          return;
>> +    }
> 
> the brace placement is inconsistant relative to the existing

oops, fixed.

> 
> 
>>  
>> +    /* Skip the vbr tag frame */
>> +    url_fseek(s->pb, base + vbrtag_size, SEEK_SET);
>> +
>>      spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
>>      st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
>>                                  st->time_base);
> 
>> @@ -452,7 +465,6 @@
>>      AVStream *st;
>>      uint8_t buf[ID3v1_TAG_SIZE];
>>      int len, ret, filesize;
>> -    int64_t off;
>>  
>>      st = av_new_stream(s, 0);
>>      if (!st)
>> @@ -492,9 +504,7 @@
>>          url_fseek(s->pb, 0, SEEK_SET);
>>      }
>>  
>> -    off = url_ftell(s->pb);
>> -    mp3_parse_vbr_tags(s, st, off);
>> -    url_fseek(s->pb, off, SEEK_SET);
>> +    mp3_parse_vbr_tags(s, st, url_ftell(s->pb));
> 
> url_ftell() can be called in mp3_parse_vbr_tags()

Removed base param from mp3_parse_vbr_tags, now url_ftell is called from 
within.


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