[FFmpeg-soc] [Patch]MXF muxer version 0.0.3

[Michael Niedermayer]

On Tue, Aug 19, 2008 at 08:45:54PM +0800, zhentan feng wrote:
> Hi
> 
> 2008/8/19 Michael Niedermayer <michaelni at gmx.at>
[...]
> > [...]
> > > +static int mxf_write_track(AVFormatContext *s, int stream_index, enum
> > MXFMetadataSetType type, int *track_number_sign)
> > > +{
> > > +    ByteIOContext *pb = s->pb;
> > > +    AVStream *st;
> > > +    MXFStreamContext *sc;
> > > +    const MXFCodecUL *element;
> > > +    int i = 0;
> > > +
> > > +    mxf_write_metadata_key(pb, 0x013b00);
> > > +#ifdef DEBUG
> > > +    PRINT_KEY(s, "track key", pb->buf_ptr - 16);
> > > +#endif
> > > +    klv_encode_ber_length(pb, 80);
> > > +
> > > +    st = s->streams[stream_index];
> > > +    sc = st->priv_data;
> > > +
> > > +    // write track uid
> > > +    mxf_write_local_tag(pb, 16, 0x3C0A);
> > > +    mxf_write_uuid(pb, Track * type, stream_index);
> > > +#ifdef DEBUG
> > > +    PRINT_KEY(s, "track uid", pb->buf_ptr - 16);
> > > +#endif
> > > +    // write track id
> > > +    mxf_write_local_tag(pb, 4, 0x4801);
> > > +    put_be32(pb, stream_index);
> > > +
> >
> > > +    mxf_write_local_tag(pb, 4, 0x4804);
> > > +    if (type != MaterialPackage) {
> > > +        for (element = mxf_essence_element_key; element->id !=
> > CODEC_ID_NONE; element++) {
> > > +            if (st->codec->codec_id== element->id) {
> > > +                // write track number
> > > +                put_buffer(pb, element->uid + 12, 3);
> > > +                put_byte(pb, element->uid[15] + track_number_sign[i]);
> > > +                track_number_sign[i] ++;
> > > +
> > > +                // set essence_element key
> >
> > > +                memcpy(sc->track_essence_element_key, element->uid, 16);
> >
> > shouldnt [15] of track_essence_element_key be set to track_number_sign[i]
> > as
> > well?
> >
> I am not clear about your suggestion, could you please explain more?
> thanks.
> 
> and I explain my intention here:
> last 4 bytes of essence element key is the track number.
> the last byte ,ie byte 16, is the index of different essence element to
> distinguish different track has the same element key.
> 
> track_number_sign[i] record the  times of  the "i"th element key, when meet
> the same element key , track_number_sign[i]++ , and be added on
> track_essence_element[15], so the whole 16 bytes are used as element key.

sc->track_essence_element_key is a copy of element->uid
element->uid is from a static const table, thus it does not contain the
"track number".
The track number was just directly stored here with put_byte() it is missing
from sc->track_essence_element_key


> 
> 
> > > +                break;
> > > +            }
> > > +            i++;
> > > +        }
> > > +    } else {
> > > +        put_be32(pb, 0); // track number of material package is 0
> > > +    }
> > > +
> > > +    mxf_write_local_tag(pb, 8, 0x4B01);
> > > +    put_be32(pb, st->time_base.den);
> > > +    put_be32(pb, st->time_base.num);
> > > +
> > > +    // write origin
> > > +    mxf_write_local_tag(pb, 8, 0x4B02);
> > > +    put_be64(pb, 0);
> > > +
> > > +    // write sequence refs
> > > +    mxf_write_local_tag(pb, 16, 0x4803);
> >
> > > +    mxf_write_uuid(pb, Sequence * Track * type, stream_index);
> >
> > Is it intended to multiply the values of 2 enums with the type ?
> >
> yes. we choose the value of the enum represent the type of the metadata set.
> it will generate a type to represent Sequence set, because the enum value of
> Sequence is not big enough, it may confilict with other metadata set.

mxf_write_uuid(pb, type==SourcePackage ? FooBar : BarFoo, stream_index);
seems much cleaner to me
also it is less likely to break when more enums are added and something
else happens to match Sequence * Track * type

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus
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