[FFmpeg-devel] [PATCH v3] Canopus Lossless decoder

Michael Niedermayer michaelni at gmx.at
Sun Jul 29 04:23:59 CEST 2012


On Sat, Jul 28, 2012 at 06:28:50PM -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>
> ---
>  Changelog              |    1 +
>  MAINTAINERS            |    1 +
>  doc/general.texi       |    1 +
>  libavcodec/Makefile    |    1 +
>  libavcodec/allcodecs.c |    1 +
>  libavcodec/avcodec.h   |    1 +
>  libavcodec/cllc.c      |  290 ++++++++++++++++++++++++++++++++++++++++++++++++
>  libavcodec/version.h   |    2 +-
>  libavformat/riff.c     |    1 +
>  9 files changed, 298 insertions(+), 1 deletion(-)
>  create mode 100644 libavcodec/cllc.c
> 
> diff --git a/Changelog b/Changelog
> index 79a8f4c..813116a 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -38,6 +38,7 @@ version next:
>  - alphaextract and alphamerge filters
>  - concat filter
>  - flite filter
> +- Canopus Lossless Codec decoder
>  
>  
>  version 0.11:
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 1a9f29b..f265907 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -132,6 +132,7 @@ Codecs:
>    celp_filters.*                        Vitor Sessak
>    cinepak.c                             Roberto Togni
>    cljr                                  Alex Beregszaszi
> +  cllc.c                                Derek Buitenhuis
>    cook.c, cookdata.h                    Benjamin Larsson
>    crystalhd.c                           Philip Langdale
>    cscd.c                                Reimar Doeffinger
> diff --git a/doc/general.texi b/doc/general.texi
> index 1849aec..ebbe189 100644
> --- a/doc/general.texi
> +++ b/doc/general.texi
> @@ -501,6 +501,7 @@ following image formats are supported:
>  @item Delphine Software International CIN video  @tab     @tab  X
>      @tab Codec used in Delphine Software International games.
>  @item Discworld II BMV Video @tab     @tab  X
> + at item Canopus Lossless Codec @tab     @tab  X
>  @item Cinepak                @tab     @tab  X
>  @item Cirrus Logic AccuPak   @tab  X  @tab  X
>      @tab fourcc: CLJR
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index b4138e8..bb9aa9a 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -131,6 +131,7 @@ OBJS-$(CONFIG_CDXL_DECODER)            += cdxl.o
>  OBJS-$(CONFIG_CINEPAK_DECODER)         += cinepak.o
>  OBJS-$(CONFIG_CLJR_DECODER)            += cljr.o
>  OBJS-$(CONFIG_CLJR_ENCODER)            += cljr.o
> +OBJS-$(CONFIG_CLLC_DECODER)            += cllc.o
>  OBJS-$(CONFIG_COOK_DECODER)            += cook.o
>  OBJS-$(CONFIG_CSCD_DECODER)            += cscd.o
>  OBJS-$(CONFIG_CYUV_DECODER)            += cyuv.o
> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> index 6bcc3c2..43c6c16 100644
> --- a/libavcodec/allcodecs.c
> +++ b/libavcodec/allcodecs.c
> @@ -94,6 +94,7 @@ void avcodec_register_all(void)
>      REGISTER_DECODER (CDXL, cdxl);
>      REGISTER_DECODER (CINEPAK, cinepak);
>      REGISTER_ENCDEC  (CLJR, cljr);
> +    REGISTER_DECODER (CLLC, cllc);
>      REGISTER_DECODER (CSCD, cscd);
>      REGISTER_DECODER (CYUV, cyuv);
>      REGISTER_DECODER (DFA, dfa);
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index edbc59b..b7f4a41 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -274,6 +274,7 @@ enum CodecID {
>      CODEC_ID_YUV4       = MKBETAG('Y','U','V','4'),
>      CODEC_ID_SANM       = MKBETAG('S','A','N','M'),
>      CODEC_ID_PAF_VIDEO  = MKBETAG('P','A','F','V'),
> +    CODEC_ID_CLLC       = MKBETAG('C','L','L','C'),
>  
>      /* various PCM "codecs" */
>      CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the start of audio codecs
> diff --git a/libavcodec/cllc.c b/libavcodec/cllc.c
> new file mode 100644
> index 0000000..586361d
> --- /dev/null
> +++ b/libavcodec/cllc.c
> @@ -0,0 +1,290 @@
> +/*
> + * Canopus Lossless Codec decoder
> + *
> + * Copyright (c) 2012 Derek Buitenhuis
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg 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.
> + *
> + * FFmpeg 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 FFmpeg; 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;
> +    int      swapped_buf_size;
> +    int8_t   code_table[3][32768];
> +} CLLCContext;
> +
> +/*
> + * We could use ff_init_vlc_sparse and get_vlc2, but it would

> + * provide basolutely no benefit in this case. The lookup table

basolutely ?

[...]
> +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;
> +    pred = *top_left;
> +
> +    /* 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);
> +
> +        dst[0] = pred;
> +        dst   += 3;
> +    }

for strict correctness pred should be a unsigned type, due to overflow
i dont think it makes any difference in practice though

also if you want maximum speed GET_VLC() should be faster but the
code would be more messy, get_vlc2() is a compromise

these functions can also use a single table or use a smaller first
level table (that fits in the L1 cache of your CPU) and only touch
the 2nd level for less common longer vlc codes. Which of these
2 variants if faster depends on input data and cpu


[...]
> +static av_cold int cllc_decode_close(AVCodecContext *avctx)
> +{
> +    CLLCContext *ctx = avctx->priv_data;
> +
> +    if (avctx->coded_frame->data[0])
> +        avctx->release_buffer(avctx, avctx->coded_frame);
> +
> +    if (avctx->coded_frame)
> +        av_freep(&avctx->coded_frame);
> +
> +    if (ctx->swapped_buf)
> +        av_freep(&ctx->swapped_buf);

the if() are unneeded

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

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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