[FFmpeg-devel] [PATCH]lavf/mov: Support alac extradata in wave atom v2

[Michael Niedermayer]

On Wed, Aug 05, 2015 at 11:52:43PM +0200, Carl Eugen Hoyos wrote:
> On Wednesday 05 August 2015 02:39:38 pm Michael Niedermayer wrote:
> > On Mon, Aug 03, 2015 at 11:16:12PM +0200, Carl Eugen Hoyos wrote:
> > > Hi!
> > >
> > > Attached patch fixes ticket #4747 and should not introduce any
> > > theoretical regressions.
> > >
> > > Please review, Carl Eugen
> > >
> > >  mov.c |   22 ++++++++++++++++++++++
> > >  1 file changed, 22 insertions(+)
> > > ffe1a030382f6bc11a5a58ab3cd5e89f8a354529  patchalacwave2.diff
> > > diff --git a/libavformat/mov.c b/libavformat/mov.c
> > > index 154d2f8..f3cb71f 100644
> > > --- a/libavformat/mov.c
> > > +++ b/libavformat/mov.c
> > > @@ -1435,6 +1435,28 @@ static int mov_read_wave(MOVContext *c,
> > > AVIOContext *pb, MOVAtom atom) if (ret < 0)
> > >              return ret;
> > >      } else if (atom.size > 8) { /* to read frma, esds atoms */
> > > +        if (st->codec->codec_id == AV_CODEC_ID_ALAC && atom.size >= 24)
> > > { +            uint64_t buffer = avio_rb64(pb);
> > > +            atom.size -= 8;
> > > +            if (  (buffer & 0xFFFFFFFF) == MKBETAG('f','r','m','a')
> > > +                && buffer >> 32 <= atom.size
> > > +                && buffer >> 32 >= 8) {
> > > +                avio_skip(pb, (buffer >> 32) - 8);
> > > +                atom.size -= (buffer >> 32) - 8;
> >
> > skiping the frma atom instead of passing it to mov_read_default()
> > (which might at some point in the future do somehing with it)
> > does not feel completely ideal
> 
> New patch attached.
> 
> Thank you, Carl Eugen

>  mov.c |   21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> d078903c9066e864496f9f29d8761030f001a1d7  patchalacwave3.diff
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 154d2f8..157c5c1 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -1417,7 +1417,8 @@ static int mov_read_svq3(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>  static int mov_read_wave(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>  {
>      AVStream *st;
> -    int ret;
> +    int ret, seek_back = 0;
> +    int64_t position;
>  
>      if (c->fc->nb_streams < 1)
>          return 0;
> @@ -1435,8 +1436,26 @@ static int mov_read_wave(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>          if (ret < 0)
>              return ret;
>      } else if (atom.size > 8) { /* to read frma, esds atoms */
> +        if (   st->codec->codec_id == AV_CODEC_ID_ALAC
> +            && atom.size >= 24
> +            && !ffio_ensure_seekback(pb, atom.size)) {
> +            seek_back = 1;
> +            position = avio_tell(pb);
> +        }
>          if ((ret = mov_read_default(c, pb, atom)) < 0)
>              return ret;
> +        if (seek_back && !st->codec->extradata_size) {
> +            av_assert0(position == avio_seek(pb, position, SEEK_SET));
> +#define ALAC_EXTRADATA_SIZE 36
> +            st->codec->extradata = av_mallocz(ALAC_EXTRADATA_SIZE + AV_INPUT_BUFFER_PADDING_SIZE);
> +            if (!st->codec->extradata)
> +                return AVERROR(ENOMEM);
> +            st->codec->extradata_size = ALAC_EXTRADATA_SIZE;
> +            AV_WB32(st->codec->extradata    , ALAC_EXTRADATA_SIZE);
> +            AV_WB32(st->codec->extradata + 4, MKTAG('a','l','a','c'));
> +            avio_read(pb, st->codec->extradata + 12, 24);
> +            avio_skip(pb, atom.size - 24);
> +        }

this assumes that mov_read_default() does not seek outside the atom

i had more thought about something like below
but maybe iam missing something


@@ -1435,6 +1435,28 @@ static int mov_read_wave(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         if (ret < 0)
             return ret;
     } else if (atom.size > 8) { /* to read frma, esds atoms */
+        if (st->codec->codec_id == AV_CODEC_ID_ALAC && atom.size >= 24) {
+            uint64_t buffer;
+            ffio_ensure_seekback(pb, 8);
+            buffer = avio_rb64(pb);
+            atom.size -= 8;
+            if (  (buffer & 0xFFFFFFFF) == MKBETAG('f','r','m','a')
+                && buffer >> 32 <= atom.size
+                && buffer >> 32 >= 8) {
+                avio_skip(pb,  - 8);
+                atom.size += 8;
+            } else if (!st->codec->extradata_size) {
+#define ALAC_EXTRADATA_SIZE 36
+                st->codec->extradata = av_mallocz(ALAC_EXTRADATA_SIZE + AV_INPUT_BUFFER_PADDING_SIZE);
+                if (!st->codec->extradata)
+                    return AVERROR(ENOMEM);
+                st->codec->extradata_size = ALAC_EXTRADATA_SIZE;
+                AV_WB32(st->codec->extradata     , ALAC_EXTRADATA_SIZE);
+                AV_WB32(st->codec->extradata +  4, MKTAG('a','l','a','c'));
+                AV_WB64(st->codec->extradata + 12, buffer);
+                avio_read(pb, st->codec->extradata + 20, 16);
+                avio_skip(pb, atom.size - 24);
+                return 0;
+            }
+        }
         if ((ret = mov_read_default(c, pb, atom)) < 0)
             return ret;
     } else






>      } else
>          avio_skip(pb, atom.size);
>      return 0;

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-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are best at talking, realize last or never when they are wrong.
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