[Ffmpeg-devel] [RFC] Musepack decoding support

[Michael Niedermayer]

Hi

On Thu, Dec 21, 2006 at 08:12:16AM +0200, Kostya wrote:
> Here is updated decoder and demuxer.
> And again about seeking: now it just builds index as it goes,

[...]
> +    GetBitContext gb;
> +    uint8_t buf[8];
> +    float f1=1.20050805774840750476 * 256;
> +    static int vlc_inited = 0;
> +
> +    if(avctx->extradata_size < 8){
> +        av_log(avctx, AV_LOG_ERROR, "Too small extradata size (%i)!\n", avctx->extradata_size);
> +        return -1;
> +    }
> +    memset(c->oldDSCF, 0, sizeof(c->oldDSCF));
> +    c->rnd = 0xDEADBEEF;
> +    dsputil_init(&c->dsp, avctx);
> +    c->dsp.bswap_buf(buf, avctx->extradata, 2);

hmm doesnt the argument to bswap_buf() need to be aligned by more?


> +    ff_mpa_synth_init(mpa_window);
> +    init_get_bits(&gb, buf, 64);
> +
> +    c->IS = get_bits1(&gb);
> +    c->MSS = get_bits1(&gb);
> +    c->bands = get_bits(&gb, 6);
> +    if(c->bands >= BANDS){
> +        av_log(avctx, AV_LOG_ERROR, "Too many bands: %i\n", c->bands);
> +        return -1;
> +    }
> +    skip_bits(&gb, 88);
> +    c->gapless = get_bits1(&gb);
> +    c->lastframelen = get_bits(&gb, 11);

something is wrong here, 1+1+6+88+1+11 > 64 ...


[...]
> +/**
> + * Process decoded Musepack data and produce PCM
> + * TODO make it available for MPC8 and MPC6

nitpick: i think doxygen had a special tag for todo items maybe @todo ?


[...]
> +    /* get quantizers */
> +    memset(Q, 0, sizeof(Q));
> +    off = 0;
> +    for(i = 0; i < BANDS; i++, off += SAMPLES_PER_BAND)
> +        for(ch = 0; ch < 2; ch++)
> +            idx_to_quant(c, &gb, bands[i].res[ch], Q[ch] + off);

hmm, isnt Q[ch] always 0 here?


[...]
> +    t = get_le32(&s->pb);
> +    if((t & 0xFFFFFF) != MKTAG('M', 'P', '+', 0)){
> +        av_log(s, AV_LOG_ERROR, "Not a Musepack file\n");
> +        return -1;
> +    }
> +    c->ver = t >> 24;

if(get_le24(&s->pb) != MKTAG('M', 'P', '+', 0)){
    av_log(s, AV_LOG_ERROR, "Not a Musepack file\n");
    return -1;
}
c->ver = get_byte(&s->pb);


[...]
> +    get_buffer(&s->pb, buf, 16);
> +    t = LE_32(buf);
> +    samplerate = mpc_rate[(t >> 16) & 3];
> +
> +    c->curbits = 8;
> +
> +    st = av_new_stream(s, 0);
> +    av_set_pts_info(st, 32, MPC_FRAMESIZE, samplerate);
> +    if (!st)
> +        return AVERROR_NOMEM;
> +    st->codec->codec_type = CODEC_TYPE_AUDIO;
> +    st->codec->codec_id = CODEC_ID_MUSEPACK7;
> +    st->codec->channels = 2;
> +    st->codec->sample_rate = samplerate;
> +    st->codec->bits_per_sample = 16;
> +
> +    st->codec->extradata_size = 16;
> +    st->codec->extradata = av_mallocz(st->codec->extradata_size+FF_INPUT_BUFFER_PADDING_SIZE);
> +    memcpy(st->codec->extradata, buf, 16);

c= st->codec;
c->extradata_size = 16;
c->extradata = av_mallocz(c->extradata_size+FF_INPUT_BUFFER_PADDING_SIZE);
get_buffer(&s->pb, c->extradata, 16);
c->sample_rate = mpc_rate[c->extradata[2] & 3];

?


[...]
> +    if (av_new_packet(pkt, size) < 0)
> +        return AVERROR_IO;
> +
> +    pkt->data[0] = curbits;
> +    pkt->data[1] = (c->curframe > c->fcount);
> +    pkt->data[2] = seeked;

uhm, this is ugly ...

to detect seeking in the decoder theres AVCodec.flush() which must be
called by the application when seeking ...
the other 2 are ugly too but i dunno how to avoid them ...


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Democracy is the form of government in which you can choose your dictator
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20061223/773faa3d/attachment.pgp>