[FFmpeg-devel] Suggestion for a centralized language-tag facility in libavformat

[Michael Niedermayer]

On Wed, Apr 22, 2009 at 05:16:13PM +0200, cyril comparon wrote:
> >> Sure thing. I wrote it using Qt4. Please find it attached
> >> (iso639tool.cpp, iso639tool.pro, iso639tool.readme).
> > there seem to be only 2 patches attached
> 
> Oops, forgot to attach them. Here they are.
> 
> >
> > I also found no hint in the spec that would restrict what key can be, and
> > IMHO it can be anything including NULL
> >
> 
> I got rid of the temporary key object and I changed the comparison
> function to interpret its lhs arg directly as a const char* ; it seems
> to work properly with my tests but I am not sure this will work with
> all stdlib implementations...
> 
> >> + ? ? ? ? ? ?stream_language_index = asf->streams[i].stream_language_index;
> >> + ? ? ? ? ? ?rfc1766 = asf->stream_languages[stream_language_index];
> >
> > this still reads outside the array
> 
> I think I got messed up with my different patch versions...
> 
> Thanks for your time
> Cyril


>  Changelog                |    1 
>  libavformat/avlanguage.c |  764 +++++++++++++++++++++++++++++++++++++++++++++++
>  libavformat/avlanguage.h |   39 ++
>  3 files changed, 804 insertions(+)

patch ok


[...]
> @@ -442,6 +444,58 @@
>          end_header(pb, hpos);
>      }
>  
> +    /* stream extension headers */
> +    for(n=0; n<s->nb_streams; n++) {
> +        enum Flags {
> +            reliable_flag = 1,
> +            seekable_flag = 2,
> +            no_cleanpoints_flag = 4,
> +            resend_live_cleanpoints_flag = 8
> +        } flags = 0;
> +        hpos = put_header(pb, &ff_asf_ext_stream_header);
> +        put_le64(pb, 0); // starttime (optional so zero to ignore it)
> +        put_le64(pb, 0); // endtime (optional so zero to ignore it)
> +        AVStream *st = s->streams[n];

Mixing declarations and statements breaks gcc 2.95


> +        put_le32(pb, st->codec->bit_rate); // leak-datarate
> +        put_le32(pb, BUFFER_SIZE_IN_MS); // bucket-datasize
> +        put_le32(pb, 0); // init-bucket-fullness
> +        put_le32(pb, st->codec->bit_rate); // alt-leak-datarate
> +        put_le32(pb, BUFFER_SIZE_IN_MS); // alt-bucket-datasize in milliseconds
> +        put_le32(pb, 0); // alt-init-bucket-fullness
> +        put_le32(pb, 0); // max-object-size (zero means unknown)
> +        if (asf->nb_index_count > 0)
> +            flags |= seekable_flag; // key-frames are present so the stream is seekable
> +        else
> +            flags |= no_cleanpoints_flag; // no key-frames
> +        put_le32(pb, flags); // flags (reliable,seekable,no_cleanpoints,resend_live_cleanpoints, rest of bits reserved)
> +        put_le16(pb, asf->streams[n].num); // stream-num
> +        put_le16(pb, n); // stream-language-id-index
> +        put_le64(pb, 0); // avg frametime in 100ns units (zero means unknown)
> +        put_le16(pb, 0); // stream-name-count
> +        put_le16(pb, 0); // payload-extension-system-count
> +        end_header(pb, hpos);
> +    }
> +
> +    /* language list */
> +    hpos = put_header(pb, &ff_asf_language_guid);
> +    for(nbStreamsWithSupportedLang=0, n=0; n<s->nb_streams; n++) {
> +        AVMetadataTag *lang_tag = av_metadata_get(s->streams[n]->metadata, "language", NULL, 0);
> +        if (lang_tag && av_convertLangTo(lang_tag->value, AV_LANG_ISO639_1))
> +            nbStreamsWithSupportedLang++;
> +    }
> +    put_le16(pb, nbStreamsWithSupportedLang);
> +    for(n=0; n<s->nb_streams; n++) {
> +        AVMetadataTag *lang_tag = av_metadata_get(s->streams[n]->metadata, "language", NULL, 0);
> +        if (lang_tag) {
> +            const char *language = av_convertLangTo(lang_tag->value, AV_LANG_ISO639_1);
> +            if (language) {
> +                put_byte(pb, 2*(1+strlen(language)));
> +                put_str16_nolen(pb, language);
> +            }
> +        }
> +    }

This still does not look like it would work where any of these if() false once

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

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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