[FFmpeg-devel] [PATCH] read metadata in FLAC demuxer

[Michael Niedermayer]

On Sun, Sep 30, 2007 at 12:48:08AM -0400, Justin Ruggles wrote:
> Hi,
>
> Here is a patch to fix issue 187 in the FFmpeg Issue Tracker, "flac decoder 
> fails with large metadata".
>
> For raw FLAC files, the metadata header(s) are read in the demuxer rather 
> than the decoder.  This correctly skips any irrelevant metadata blocks, and 
> it also parses vorbiscomment info.

what happens with flac in avi and matroska ?


[...]

> +    /* create AVStream */
>      st = av_new_stream(s, 0);

cosmetic


>      if (!st)
>          return AVERROR(ENOMEM);
>      st->codec->codec_type = CODEC_TYPE_AUDIO;
>      st->codec->codec_id = CODEC_ID_FLAC;
> -    st->need_parsing = AVSTREAM_PARSE_FULL;
> -    /* the parameters will be extracted from the compressed bitstream */
> +
> +    /* verify fLaC tag */
> +    if(get_be32(pb) != MKBETAG('f','L','a','C'))
> +        return -1;
> +
> +    /* read metadata blocks */
> +    do {
> +        int tmp, type, size;
> +        tmp = get_byte(pb);
> +        last_metablock = tmp >> 7;
> +        type = tmp & 0x7F;
> +        size = get_be24(pb);
> +        if(size) {
> +            if(type == 0) {
> +                /* read streaminfo to codec extradata */
> +                GetBitContext gb;
> +                int64_t samples;
> +                st->codec->extradata = av_malloc(FLAC_STREAMINFO_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
> +                get_buffer(pb, st->codec->extradata, size);
> +                init_get_bits(&gb, st->codec->extradata, FLAC_STREAMINFO_SIZE*8);
> +
> +                skip_bits(&gb, 16*2+24*2);
> +                st->codec->sample_rate = get_bits_long(&gb, 20);
> +                st->codec->channels = get_bits(&gb, 3) + 1;
> +                skip_bits(&gb, 5);
> +                samples = get_bits(&gb, 4);
> +                samples = (samples << 32) | get_bits_long(&gb, 32);
> +                if(!st->codec->sample_rate) {
> +                    av_freep(&st->codec->extradata);
> +                    return -1;
> +                }
> +                st->codec->extradata_size = FLAC_STREAMINFO_SIZE;
> +                av_set_pts_info(st, 64, 1, st->codec->sample_rate);
> +                if(samples) {
> +                    s->start_time = 0;
> +                    s->duration = samples * AV_TIME_BASE / st->codec->sample_rate;
> +                }
> +            } else if(type == 4) {
> +                /* read and parse vorbiscomment metadata block */
> +                uint8_t *vorbiscomment = av_malloc(size);
> +                get_buffer(pb, vorbiscomment, size);
> +                vorbis_comment(s, vorbiscomment, size);
> +                av_freep(&vorbiscomment);
> +            } else {
> +                url_fskip(pb, size);
> +            }
> +        }
> +    } while(!last_metablock);

also thats duplicating code (from the decoder)

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

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
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