[FFmpeg-devel] [PATCH] Canopus Lossless decoder

Michael Niedermayer michaelni at gmx.at
Sat Jul 28 03:51:39 CEST 2012


On Fri, Jul 27, 2012 at 07:18:25PM -0400, Derek Buitenhuis wrote:
> At the moment it only does BGR24, but I plan to add the rest after.
> 
> Signed-off-by: Derek Buitenhuis <derek.buitenhuis at gmail.com>
[...]
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index edbc59b..bd3e8f3 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -261,6 +261,7 @@ enum CodecID {
>      CODEC_ID_MSA1,
>      CODEC_ID_TSCC2,
>      CODEC_ID_MTS2,
> +    CODEC_ID_CLLC,
>      CODEC_ID_Y41P       = MKBETAG('Y','4','1','P'),
>      CODEC_ID_ESCAPE130  = MKBETAG('E','1','3','0'),
>      CODEC_ID_EXR        = MKBETAG('0','E','X','R'),

this has a high chance to break compatibility of the codec ids between
forks
    

> diff --git a/libavcodec/cllc.c b/libavcodec/cllc.c
> new file mode 100644
> index 0000000..03e6937
> --- /dev/null
> +++ b/libavcodec/cllc.c
> @@ -0,0 +1,276 @@
> +/*
> + * Canopus Lossless Codec decoder
> + *
> + * Copyright (c) 2012 Derek Buitenhuis
> + *
> + * This file is part of Libav.

wrong project


> + *
> + * Libav is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * Libav is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with Libav; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include "libavutil/intreadwrite.h"
> +#include "dsputil.h"
> +#include "get_bits.h"
> +#include "avcodec.h"
> +
> +typedef struct CLLCContext {
> +    DSPContext dsp;
> +    AVCodecContext *avctx;
> +
> +    uint8_t *swapped_buf;
> +    int8_t  *code_table[3];
> +} CLLCContext;
> +
> +static int read_code_table(GetBitContext *gb, int8_t *code_table)
> +{
> +    int num_lens, num_lens_orig;
> +    int num_codes;
> +    int prefix, symbol;
> +    int sym_shift;
> +    int i, j, k;
> +
> +    sym_shift = 13;
> +    prefix    = 0;
> +
> +    num_lens = num_lens_orig = get_bits(gb, 5);
> +
> +    for (i = 0; i < num_lens; i++) {
> +        num_codes = get_bits(gb, 9);
> +
> +        for (j = num_codes; j > 0; j--) {
> +            symbol = get_bits(gb, 8);
> +
> +            for (k = prefix << sym_shift; k < prefix + 1 << sym_shift; k++) {
> +                code_table[2 * k]     = symbol;
> +                code_table[2 * k + 1] = i + 1;
> +            }

looks like it can overwrite the buffer


> +
> +            prefix++;
> +        }
> +

> +        if (num_codes)
> +            num_lens = num_lens_orig;

does nothing


> +
> +        sym_shift--;
> +        prefix <<= 1;
> +    }


> +
> +    return num_lens;
> +}
> +
> +static int read_line(CLLCContext *ctx, GetBitContext *gb, int *top_left,
> +                     int8_t *code_table, uint8_t *outbuf)
> +{
> +    uint8_t *dst;
> +    int pred, skip;
> +    int i;
> +
> +    dst = outbuf;
> +
> +    /* Stash the first pixel */
> +    pred = *top_left = *top_left + code_table[2 * show_bits(gb, 14)];
> +
> +    /* Simultaniously read and restore the line */
> +    for (i = 0; i < ctx->avctx->width; i++) {
> +        pred += code_table[2 * show_bits(gb, 14)];
> +        skip  = code_table[2 * show_bits(gb, 14) + 1];
> +
> +        skip_bits(gb, skip);

this looks like a reimplementation of get_vlc*


> +
> +        dst[0] = pred;
> +        dst   += 3;
> +    }
> +
> +    return 0;
> +}
> +
> +static int decode_bgr24_frame(CLLCContext *ctx, GetBitContext *gb, AVFrame *pic)
> +{
> +    AVCodecContext *avctx = ctx->avctx;
> +    uint8_t *dst;
> +    int pred[3];
> +    int ret;
> +    int i, j;
> +
> +    pred[0] =   128;
> +    pred[1] =   128;
> +    pred[2] =  -128;
> +
> +    dst = pic->data[0] + 5;
> +
> +    skip_bits(gb, 16);
> +
> +    /* Read in code table for each plane */
> +    for (i = 0; i < 3; i++) {
> +        ret = read_code_table(gb, ctx->code_table[i]);
> +        if (ret <= 0) {
> +            av_log(ctx->avctx, AV_LOG_ERROR,
> +                   "Could not read code table %d.\n", i);
> +            return ret;
> +        }
> +    }
> +
> +    /* Read in and restore every lie */
> +    for (i = avctx->height; i > 0; i--) {
> +        for (j = 0; j < 3; j++)
> +            read_line(ctx, gb, &pred[j], ctx->code_table[j], dst - j);
> +
> +        dst += pic->linesize[0];
> +    }
> +
> +    return 0;
> +}
> +
> +static int cllc_decode_frame(AVCodecContext *avctx, void *data,
> +                             int *data_size, AVPacket *avpkt)
> +{
> +    CLLCContext *ctx = avctx->priv_data;
> +    AVFrame *pic = avctx->coded_frame;
> +    uint8_t *src = avpkt->data;
> +    uint32_t info_tag, info_offset, coding_type;
> +    GetBitContext gb;
> +    int ret;
> +
> +    if (pic->data[0])
> +        avctx->release_buffer(avctx, pic);
> +
> +    pic->reference = 0;
> +
> +    /* Skip the INFO header if present */
> +    info_offset = 0;
> +    info_tag    = AV_RL32(src);
> +    if (info_tag == MKTAG('I', 'N', 'F', 'O')) {
> +        info_offset = AV_RL32(src + 4) + 8;
> +        src        += info_offset;
> +
> +        av_log(avctx, AV_LOG_DEBUG, "Skipping INFO chunk.\n");
> +    }
> +
> +    /* bswap16 the buffer since CLLC's bitreader works in 16-bit WORDS */
> +    ctx->dsp.bswap16_buf((uint16_t *) ctx->swapped_buf, (uint16_t *) src,
> +                         (avpkt->size - info_offset) / 2);
> +
> +    init_get_bits(&gb, ctx->swapped_buf, (avpkt->size - info_offset) * 8);
> +
> +    /*
> +     * Read in coding type. The types are as follows:
> +     *
> +     * 0 - YUY2
> +     * 1 - BGR24 (Triples)
> +     * 2 - BGR24 (Quads)
> +     * 3 - BGRA
> +     */
> +    coding_type = (AV_RL32(src) >> 8) & 0xFF;
> +    av_log(avctx, AV_LOG_DEBUG, "Frame coding type: %d\n", coding_type);

why is coding_type uint32_t ? the %d would be wrong too in that case


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

Those who are best at talking, realize last or never when they are wrong.
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