[FFmpeg-devel] [PATCH] Windows Television (.wtv) demuxer

[Peter Ross]

Updated patch set. Improvements:
    demuxer now ignores unsupported streams
    placeholder streams are also ignored
    use metadata 'language' tag
    added AC3 GUID

On Tue, Sep 28, 2010 at 09:03:33PM +0200, Michael Niedermayer wrote:
> On Tue, Sep 28, 2010 at 12:28:19AM +1000, Peter Ross wrote:
> [...]
> > +/**
> > + * parse VIDEOINFOHEADER2 structure
> > + * @return bytes consumed
> > + */
> > +static int parse_videoinfoheader2(AVFormatContext *s, AVStream *st)
> > +{
> > +    ByteIOContext *pb = s->pb;
> > +
> > +    // VIDEOINFOHEADER2 part
> > +    url_fskip(pb, 32);
> > +    st->codec->bit_rate = get_le32(pb);
> > +    url_fskip(pb, 20);
> > +    st->sample_aspect_ratio.num = get_le32(pb);
> > +    st->sample_aspect_ratio.den = get_le32(pb);
> > +    url_fskip(pb, 8);
> > +
> > +    // BITMAPINFOHEADER part
> 
> we have code to read BITMAPINFOHEADERs in  libavformat/avidec.c strf
> maybe this can be factored?

Done.

> > +        url_fskip(pb, size - 32);
> > +        ff_get_guid(pb, &actual_subtype);
> > +        ff_get_guid(pb, &actual_formattype);
> 
> > +        url_fseek(pb, -size, SEEK_CUR);
> 
> this wont work with non seekable protocols

Yep it is a disadvantage. The authors of this abomination decided to write the
format identifying information (ala GUIDs) *AFTER* the format buffer.

> > +
> > +        parse_media_type(s, st, mediatype, actual_subtype, actual_formattype, size - 32);
> > +        url_fskip(pb, 32);
> > +        return;
> > +    } else if (!ff_guidcmp(mediatype, mediatype_audio)) {
> > +        if (!ff_guidcmp(formattype, format_waveformatex)) {
> > +            ff_get_wav_header(pb, st->codec, size);
> > +        } else {
> 
> > +            if (ff_guidcmp(formattype, format_none)) {
> > +                av_log(s, AV_LOG_WARNING, "unknown formatype:");
> > +                print_guid(AV_LOG_WARNING, formattype);
> > +                av_log(0, AV_LOG_WARNING, "\n");
>                           ^
> why not s?

av_log(0,...) instructs the logger not to output the context information, allowing
text to be appended to previous log statement. For the above code, the output is:

	[foo @ 0xbeef] unknown formattype:00000000000000000000000000000000(newline)

Have fixed this anyway.

> > +        } else if (!ff_guidcmp(formattype, format_mpeg2_video)) {
> > +            int consumed = parse_videoinfoheader2(s, st);
> > +            url_fskip(pb, 4);
> > +            st->codec->extradata_size = get_le32(pb);
> > +            url_fskip(pb, 12);
> > +#if 1
> > +            //the extradata is rejected by the decoder
> > +            st->codec->extradata_size = 0;
> > +#endif
> > +            if (st->codec->extradata_size) {
> > +                st->codec->extradata= av_malloc(st->codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);
> > +                if (!st->codec->extradata) {
> > +                    st->codec->extradata_size = 0;
> > +                }else {
> > +                    memset(st->codec->extradata, 0,  st->codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);
> > +                    get_buffer(pb, st->codec->extradata, st->codec->extradata_size); 
> > +                }
> 
> > +{ int i;
> > +      av_log(0,0, "data [[\n");
> > +  for(i=0; i<st->codec->extradata_size;i++) {
> > +      av_log(0,0, " %02x", st->codec->extradata[i]);
> > +  }
> > +      av_log(0,0, "]]\n");
> > +}

Cruft removed.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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