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

[Alex Converse]

On Sun, Jan 18, 2009 at 12:11 PM, Robert Swain <robert.swain at gmail.com> wrote:
> 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?

id3v2-all.diff still seems to apply cleanly. But it was missing a
dependency on id3v2.o for the mpc demuxer. So I've added that.

--Alex
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