[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.
> 
Attached is a single patch for the prevention of reading ID3v1 as part 
of a packet.

>> @@ -505,10 +515,20 @@
>>  static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
>>  {
>>      int ret, size;
>> +    int64_t size_left;
>>      //    AVStream *st = s->streams[0];
>>  
>>      size= MP3_PACKET_SIZE;
>>  
>> +    /* if we're nearing the end of the input and there's an
>> +       ID3v1 tag then make sure we don't read it as a packet */
>> +    if (((MPAContext*)s->priv_data)->found_id3v1 && s->file_size && 
>> +        (size_left = s->file_size - url_ftell(s->pb) - ID3v1_TAG_SIZE) < size) {
>> +        size = size_left;
>> +        if (size <= 0)
>> +            return AVERROR(EIO);
>> +    }
>> +
>>      ret= av_get_packet(s->pb, pkt, size);
>>  
>>      pkt->stream_index = 0;
> 
> file_size is not known for stdin/pipes

That's why I put the '&& s->file_size' so that this logic will be 
avoided when file size is not known. In any case the found_id3v1 will be 
false in such cases. But for future compatibility in case the tag will 
somehow be known but not the file size I added the '&& s->file_size' 
(which is set to 0 if file size is not known).

-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: skip_id3v1_parse.patch
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20081113/d4536ab3/attachment.txt>