[FFmpeg-devel] [PATCH] ADTS AAC with ID3v2

[Robert Swain]

2009/1/16 Michael Niedermayer <michaelni at gmx.at>:
> On Fri, Jan 16, 2009 at 11:57:52AM -0500, Alex Converse wrote:
>> On Thu, Jan 15, 2009 at 5:31 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> > On Thu, Jan 15, 2009 at 02:37:11AM -0500, Alex Converse wrote:
>> >> On Wed, Jan 14, 2009 at 1:53 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> >> >
>> >> > On Wed, Jan 14, 2009 at 01:39:05PM -0500, Alex Converse wrote:
>> >> > > On Wed, Jan 14, 2009 at 12:57 PM, Michael Niedermayer <michaelni at gmx.at>wrote:
>> >> > >
>> >> > > > On Wed, Jan 14, 2009 at 10:17:33AM -0500, Alex Converse wrote:
>> >> > > > > On Wed, Jan 14, 2009 at 10:10 AM, Michael Niedermayer <michaelni at gmx.at
>> >> > > > >wrote:
>> >> > > > >
>> >> > > > > > On Wed, Jan 14, 2009 at 09:47:29AM -0500, Alex Converse wrote:
>> >> > > > > > > On Wed, Jan 14, 2009 at 9:17 AM, Michael Niedermayer <
>> >> > > > michaelni at gmx.at
>> >> > > > > > >wrote:
>> >> > > > > > >
>> >> > > > > > > > On Wed, Jan 14, 2009 at 12:23:00AM -0500, Alex Converse wrote:
>> >> > > > > > > > > Hi,
>> >> > > > > > > > >
>> >> > > > > > > > > The attached patch adds support to the ADTS AAC probe to detect
>> >> > > > AAC
>> >> > > > > > files
>> >> > > > > > > > > with ID3v2 tags at a higher level than the MP3 probe and the MPC
>> >> > > > > > probe.
>> >> > > > > > > > It
>> >> > > > > > > > > refactors some id3 detection from mp3.c into id3v2.c.
>> >> > > > > > > > >
>> >> > > > > > > > [...]
>> >> > > > > > > >
>> >> > > > > > > > >  #define ID3v1_TAG_SIZE 128
>> >> > > > > > > > > -
>> >> > > > > > > > >  #define ID3v1_GENRE_MAX 125
>> >> > > > > > > > >
>> >> > > > > > > > >  static const char * const id3v1_genre_str[ID3v1_GENRE_MAX + 1] =
>> >> > > > {
>> >> > > > > > > >
>> >> > > > > > > > cosmetic
>> >> > > > > > > >
>> >> > > > > > > > [...]
>> >> > > > > > > > > @@ -487,7 +472,7 @@ static int mp3_read_header(AVFormatContext
>> >> > > > *s,
>> >> > > > > > > > >      ret = get_buffer(s->pb, buf, ID3v2_HEADER_SIZE);
>> >> > > > > > > > >      if (ret != ID3v2_HEADER_SIZE)
>> >> > > > > > > > >          return -1;
>> >> > > > > > > > > -    if (id3v2_match(buf)) {
>> >> > > > > > > > > +    if (ff_id3v2_match(buf)) {
>> >> > > > > > > > >          /* parse ID3v2 header */
>> >> > > > > > > > >          len = ((buf[6] & 0x7f) << 21) |
>> >> > > > > > > > >              ((buf[7] & 0x7f) << 14) |
>> >> > > > > > > >
>> >> > > > > > > > the split out of (ff_)id3v2_match is ok but should be a seperate
>> >> > > > patch
>> >> > > > > > > > and commit
>> >> > > > > > > >
>> >> > > > > > > > [...]
>> >> > > > > > > > >      }
>> >> > > > > > > > > -    if   (first_frames>=3) return AVPROBE_SCORE_MAX/2+1;
>> >> > > > > > > > > +    if   (first_frames>=3) return AVPROBE_SCORE_MAX/2+2;
>> >> > > > > > > > >      else if(max_frames>500)return AVPROBE_SCORE_MAX/2;
>> >> > > > > > > > >      else if(max_frames>=3) return AVPROBE_SCORE_MAX/4;
>> >> > > > > > > > >      else if(max_frames>=1) return 1;
>> >> > > > > > > >
>> >> > > > > > > > why?
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > > Just having an ID3v2 tag gives a score of AVPROBE_SCORE_MAX/2+1 for
>> >> > > > mp3.
>> >> > > > > >
>> >> > > > > > That sounds like a bug ...
>> >> > > > > >
>> >> > > > >
>> >> > > > > The comment about mpeg-ps in mp3.c made me think it was a hackish design
>> >> > > > > decision, not a bug.
>> >> > > >
>> >> > > > well one could call it that way, still the existence of hackish code is no
>> >> > > > argument to add more hackish code like the +1 -> +2
>> >> > > >
>> >> > >
>> >> > > What would be the correct solution for MP3 then? skipping the tag and trying
>> >> > > again?
>> >> >
>> >> > i think so
>> >>
>> >> I fixed the MP3 hackishness in the attached patch. I also fixed a typo
>> >> in the old patch. Once I fixed MP3, musepack became the next greedy
>> >> culprit so to prevent MP3 regressions I had to fix him too. I don't
>> >> have any MPC files with ID3v2 so that portion of that patch is
>> >> untested.
>> >>
>> >> In a related note, the tag skipper in mpc_read_header seems to not
>> >> check for a footer, which I think could be trouble.
>> > [...]
>> >> diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
>> >> index c27443b..649fafa 100644
>> >> --- a/libavformat/id3v2.c
>> >> +++ b/libavformat/id3v2.c
>> >> @@ -33,3 +33,15 @@ int ff_id3v2_match(const uint8_t *buf)
>> >>              (buf[8] & 0x80) == 0 &&
>> >>              (buf[9] & 0x80) == 0;
>> >>  }
>> >> +
>> >> +int ff_id3v2_tag_len(const uint8_t * buf)
>> >> +{
>> >> +    int len = ((buf[6] & 0x7f) << 21) +
>> >> +        ((buf[7] & 0x7f) << 14) +
>> >> +        ((buf[8] & 0x7f) << 7) +
>> >> +        (buf[9] & 0x7f) +
>> >> +        ID3v2_HEADER_SIZE;
>> >> +    if (buf[5] & 0x10)
>> >> +        len += ID3v2_HEADER_SIZE;
>> >> +    return len;
>> >> +}
>> >
>> > is this correct?
>> > i mean this does either X + ID3v2_HEADER_SIZE or X + 2*ID3v2_HEADER_SIZE
>> >
>>
>> That is my understanding.
>
> then patches ok

Hrm. I've already applied the one pertaining to AAC but now I see that
there is overlap between that one and the other ones.

Alex: Could you possibly provide another patch against trunk please?
And if you have commit rights now, you may as well commit it yourself.
:)

Regards,
Rob