[FFmpeg-devel] [PATCH 5/5] lavf: add uncodedframecrc test muxer.

[Michael Niedermayer]

On Wed, Jan 15, 2014 at 11:30:04PM +0100, Nicolas George wrote:
> Signed-off-by: Nicolas George <george at nsup.org>
> ---
>  libavformat/Makefile             |   1 +
>  libavformat/allformats.c         |   1 +
>  libavformat/avformat.h           |   6 +-
>  libavformat/uncodedframecrcenc.c | 171 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 176 insertions(+), 3 deletions(-)
>  create mode 100644 libavformat/uncodedframecrcenc.c
> 
> 
> ALSA and XVideo are great for casual testing, not so much for valgrind.
> 
> The output matches the output of framecrc for u8 audio and packed 8-bits
> video.
> 
> 
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 383f82f..704bd62 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -387,6 +387,7 @@ OBJS-$(CONFIG_TRUEHD_MUXER)              += rawenc.o
>  OBJS-$(CONFIG_TTA_DEMUXER)               += tta.o apetag.o img2.o
>  OBJS-$(CONFIG_TTY_DEMUXER)               += tty.o sauce.o
>  OBJS-$(CONFIG_TXD_DEMUXER)               += txd.o
> +OBJS-$(CONFIG_UNCODEDFRAMECRC_MUXER)     += uncodedframecrcenc.o framehash.o
>  OBJS-$(CONFIG_VC1_DEMUXER)               += rawdec.o
>  OBJS-$(CONFIG_VC1_MUXER)                 += rawenc.o
>  OBJS-$(CONFIG_VC1T_DEMUXER)              += vc1test.o
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index f1039dd..0ee2246 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -284,6 +284,7 @@ void av_register_all(void)
>      REGISTER_DEMUXER (TTA,              tta);
>      REGISTER_DEMUXER (TXD,              txd);
>      REGISTER_DEMUXER (TTY,              tty);
> +    REGISTER_MUXER   (UNCODEDFRAMECRC,  uncodedframecrc);
>      REGISTER_MUXDEMUX(VC1,              vc1);
>      REGISTER_MUXDEMUX(VC1T,             vc1t);
>      REGISTER_DEMUXER (VIVO,             vivo);
> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> index 3fe6c3e..4c03985 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -460,7 +460,7 @@ typedef struct AVOutputFormat {
>       * See av_write_uncoded_frame() for details.
>       */
>      int (*write_uncoded_frame)(struct AVFormatContext *, int stream_index,
> -                               AVFrame **frame, unsigned flags);
> +                               AVFrame *frame, unsigned flags);
>  } AVOutputFormat;
>  /**
>   * @}
> @@ -1937,8 +1937,8 @@ int av_write_uncoded_frame(AVFormatContext *s, int stream_index,
>   * To test whether it is possible to use it with a given muxer and stream,
>   * use av_write_uncoded_frame_query().
>   *
> - * The caller gives up ownership of the frame and must not access it
> - * afterwards.
> + * The caller keeps ownership of the frame and is responsible for freeing
> + * it.
>   *
>   * @return  >=0 for success, a negative code on error
>   */
> diff --git a/libavformat/uncodedframecrcenc.c b/libavformat/uncodedframecrcenc.c
> new file mode 100644
> index 0000000..99d1740
> --- /dev/null
> +++ b/libavformat/uncodedframecrcenc.c
> @@ -0,0 +1,171 @@
> +/*
> +* Copyright (c) 2013 Nicolas George
> +*
> +* 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/adler32.h"
> +#include "libavutil/avassert.h"
> +#include "libavutil/bprint.h"
> +#include "libavutil/imgutils.h"
> +#include "libavutil/pixdesc.h"
> +#include "avformat.h"
> +#include "internal.h"
> +
> +#define DEFINE_CRC_LINE(name, type, conv) \
> +static void crc_line_ ## name(unsigned *crc, void *data, unsigned size) \
> +{ \
> +    type *p = data; \
> +    unsigned a = *crc & 0xFFFF, b = *crc >> 16; \
> +    for (; size > 0; size--, p++) { \
> +        a = (a + (unsigned)(conv)) % 65521; \
> +        b = (b + a) % 65521; \
> +    } \
> +    *crc = a | (b << 16); \
> +}

please dont call adler32 a crc, (classical) crcs are cyclic, adler32
is not, consider a message with 1 bit set and the checksum appended
you cant just rotate that and still get a valid message, the checksum
is not even in the same kind of set (GF(256) vs GF(65521))
a valid message in respect to CRCs is just a polynom that has the
CRC generator as one of its factors (if you append the crc checksum
after the messsage), and there happens to be a n so that the generator
is a factor of x^n-1, but if x^n-1 contains the generator as a factor
its a valid message with correct CRC and adding 2 valid messages will
still give a valid message (for all linear codes actually) but adding
x^n-1 is just rotation
(i hope i got that proof right, as i didnt really double check this)

patch LGTM otherwise

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

During times of universal deceit, telling the truth becomes a
revolutionary act. -- George Orwell
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