[Ffmpeg-devel] [PATCH] C93 demuxer and decoder (GSoC qualification task)

[Michael Niedermayer]

Hi

On Thu, Apr 05, 2007 at 11:39:35PM +0300, Anssi Hannula wrote:
> Michael Niedermayer wrote:
> > Hi
> 
> Hi!
> 
> > On Thu, Apr 05, 2007 at 10:36:15PM +0300, Anssi Hannula wrote:
> >>>> +    ret = av_new_packet(pkt, datasize + 768 + 1);
> >>>> +    if (ret < 0)
> >>>> +        return ret;
> >>>> +    pkt->data[0] = 0;
> >>>> +
> >>>> +    ret = get_buffer(pb, pkt->data + 768 + 1, datasize);
> >>>> +    if (ret < datasize) {
> >>>> +        av_free_packet(pkt);
> >>>> +        return AVERROR_IO;
> >>>> +    }
> >>>> +
> >>>> +    datasize = get_le16(pb); /* palette size */
> >>>> +    if (datasize) {
> >>>> +        if (datasize != 768) {
> >>>> +            av_log(s, AV_LOG_ERROR, "invalid palette size %u\n", datasize);
> >>>> +            av_free_packet(pkt);
> >>>> +            return AVERROR_INVALIDDATA;
> >>>> +        }
> >>>> +        pkt->data[0] |= C93_HAS_PALETTE;
> >>>> +        ret = get_buffer(pb, pkt->data + 1, datasize);
> >>>> +        if (ret < datasize) {
> >>>> +            av_free_packet(pkt);
> >>>> +            return AVERROR_IO;
> >>>> +        }
> >>>> +    }
> >>> if there is no palette pkt->size should be decreased by 768
> >> Even when the 768 unused bytes are in the beginning of the pkt instead
> >> of the end?
> > 
> > hmm, i missed that, i just thought if the packets get stored in some other
> > container (like avi) it would be better to avoid the extra useless 768 bytes
> 
> I take it you don't think it is necessary to have the palette put in the
> end instead? 

ive no real oppinion on the order of palette & frame, iam fine with either
though i would prefer if the extra unused 768 bytes could be avoided ....


[...]
> +            case C93_8X8_2COLOR:
> +                cols[0] = *buf++;
> +                cols[1] = *buf++;
> +                for (j = 0; j < 8; j++) {
> +                    for (i = 0; i < 8; i++) {
> +                        out[(y+j)*stride+x+i] = cols[(buf[0] >> i) & 1];
> +                    }
> +                    buf++;
> +                }
> +                break;
> +
> +            case C93_4X4_2COLOR:
> +                for (y_off = 0; y_off < 8; y_off += 4) {
> +                    for (x_off = 0; x_off < 8; x_off += 4) {
> +                        colbit = 0;
> +                        cols[0] = *buf++;
> +                        cols[1] = *buf++;
> +                        colmask = bytestream_get_le16(&buf);
> +                        for (j = 0; j < 4; j++) {
> +                            for (i = 0; i < 4; i++) {
> +                                out[(y+y_off+j)*stride+x+x_off+i] =
> +                                    cols[(colmask >> colbit++) & 1];
> +                            }
> +                        }
> +                    }
> +                }
> +                break;
> +
> +            case C93_4X4_4COLOR_GRP:
> +                for (y_off = 0; y_off < 8; y_off += 4) {
> +                    for (x_off = 0; x_off < 8; x_off += 4) {
> +                        colbit = 0;
> +                        bytestream_get_buffer(&buf, cols, 4);
> +                        colmask = bytestream_get_le16(&buf);
> +                        for (j = 0; j < 4; j++) {
> +                            int curcols[2];
> +                            curcols[0] = j & 2 ? cols[3] : cols[0];
> +                            for (i = 0; i < 4; i++) {
> +                                curcols[1] = i & 2 ? cols[2] : cols[1];
> +                                out[(y+y_off+j)*stride+x+x_off+i] =
> +                                    curcols[(colmask >> colbit++) & 1];
> +                            }
> +                        }
> +                    }
> +                }
> +                break;
> +
> +            case C93_4X4_4COLOR:
> +                for (y_off = 0; y_off < 8; y_off += 4) {
> +                    for (x_off = 0; x_off < 8; x_off += 4) {
> +                        colbit = 0;
> +                        bytestream_get_buffer(&buf, cols, 4);
> +                        colmask = bytestream_get_le32(&buf);
> +                        for (j = 0; j < 4; j++) {
> +                            for (i = 0; i < 4; i++) {
> +                                out[(y+y_off+j)*stride+x+x_off+i] =
> +                                    cols[(colmask >> colbit) & 3];
> +                                colbit += 2;
> +                            }
> +                        }

the 2/4 color block draw code seems to occur 4 times, maybe that could be
simplfied?


> +                    }
> +                }
> +                break;
> +
> +            case C93_NOOP:
> +                break;
> +
> +            case C93_8X8_INTRA:
> +                for (j = 0; j < 8; j++) {
> +                    memcpy(&out[(y+j)*stride+x], buf, 8);
> +                    buf += 8;
> +                }
> +                break;
> +
> +            default:
> +                av_log(avctx, AV_LOG_ERROR, "unexpected type %x at %dx%d\n",
> +                       bt & 0x0F, x, y);
> +                return -1;
> +            }
> +            bt >>= 4;

the out+y*stride+x could be factored out like
for(y=0; y<HEIGHT; y+=8){
    out= newpic->data[0] + y*stride;
    for(x=0; x<WIDTH; x+=8){
        ...
        out+= 8;
    }
}


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

I count him braver who overcomes his desires than him who conquers his
enemies for the hardest victory is over self. -- Aristotle
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