[FFmpeg-devel] [PATCH] png parser

[Michael Niedermayer]

On Wed, Jun 10, 2009 at 11:52:34AM +0200, Peter Holik wrote:
> >>> On Thu, Jun 04, 2009 at 10:40:55AM +0200, Peter Holik wrote:
> >>>> > On Mon, Jun 01, 2009 at 12:27:52PM +0200, Peter Holik wrote:
> >>>> >> Hi!
> >>>> >>
> >>>> >> I've now reworked my patch to really parse a png for end of frame.
> >>>> >>
> >>>> >> Now you can filter out png's of any stream like
> >>>> >>
> >>>> >> cat garbage a.png garbage b.png garbage | ffmpeg -f image2pipe -vcodec png -i - c%d.png
> >>>> >>
> >>>> >> cu Peter
> >>>> >>  Makefile     |    1
> >>>> >>  allcodecs.c  |    1
> >>>> >>  png_parser.c |  124 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files
> >> changed, 126 insertions(+)
> >>>> >> 63f7cd1bb826726f1d2a9e7254410cd7ec98a81c  png-parser.patch
> >>>> >> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> >>>> >> index 14ef9f4..189231b 100644
> >>>> >> --- a/libavcodec/Makefile
> >>>> >> +++ b/libavcodec/Makefile
> >>>> >> @@ -411,6 +411,7 @@ OBJS-$(CONFIG_MLP_PARSER)              += mlp_parser.o mlp.o
> >>>> >>  OBJS-$(CONFIG_MPEG4VIDEO_PARSER)       += mpeg4video_parser.o h263.o mpeg12data.o
> >>>> mpegvideo.o
> >>>> >> error_resilience.o
> >>>> >>  OBJS-$(CONFIG_MPEGAUDIO_PARSER)        += mpegaudio_parser.o mpegaudiodecheader.o
> >>>> >> mpegaudiodata.o
> >>>> >>  OBJS-$(CONFIG_MPEGVIDEO_PARSER)        += mpegvideo_parser.o mpeg12.o mpeg12data.o
> >>>> mpegvideo.o
> >>>> >> error_resilience.o
> >>>> >> +OBJS-$(CONFIG_PNG_PARSER)              += png_parser.o
> >>>> >>  OBJS-$(CONFIG_PNM_PARSER)              += pnm_parser.o pnm.o OBJS-$(CONFIG_VC1_PARSER)
> >>         += vc1_parser.o
> >>>> >>  OBJS-$(CONFIG_VP3_PARSER)              += vp3_parser.o
> >>>> >> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c index e8d5d27..362021f 100644
> >>>> >> --- a/libavcodec/allcodecs.c
> >>>> >> +++ b/libavcodec/allcodecs.c
> >>>> >> @@ -334,6 +334,7 @@ void avcodec_register_all(void)
> >>>> >>      REGISTER_PARSER  (MPEG4VIDEO, mpeg4video);
> >>>> >>      REGISTER_PARSER  (MPEGAUDIO, mpegaudio);
> >>>> >>      REGISTER_PARSER  (MPEGVIDEO, mpegvideo);
> >>>> >> +    REGISTER_PARSER  (PNG, png);
> >>>> >>      REGISTER_PARSER  (PNM, pnm);
> >>>> >>      REGISTER_PARSER  (VC1, vc1);
> >>>> >>      REGISTER_PARSER  (VP3, vp3);
> >>>> >> diff --git a/libavcodec/png_parser.c b/libavcodec/png_parser.c new file mode 100644
> >>>> >> index 0000000..64f2356
> >>>> >> --- /dev/null
> >>>> >> +++ b/libavcodec/png_parser.c
> >>>> >> @@ -0,0 +1,124 @@
> >>>> >> +/*
> >>>> >> + * PNG parser
> >>>> >> + * Copyright (c) 2009 Peter Holik
> >>>> >> + *
> >>>> >> + * 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 + */
> >>>> >> +
> >>>> >> +/**
> >>>> >> + * @file libavcodec/png_parser.c
> >>>> >> + * PNG parser
> >>>> >> + */
> >>>> >> +
> >>>> >> +#include "parser.h"
> >>>> >> +#include "bytestream.h"
> >>>> >> +#include "png.h"
> >>>> >> +
> >>>> >> +static int png_parse(AVCodecParserContext *s, AVCodecContext *avctx, +
> >> const uint8_t **poutbuf, int *poutbuf_size, +                     const uint8_t *buf, int
> >> buf_size)
> >>>> >> +{
> >>>> >> +    ParseContext *pc = s->priv_data;
> >>>> >> +    uint8_t *bytestream;
> >>>> >> +    uint8_t *bytestream_start;
> >>>> >> +    uint8_t *bytestream_end;
> >>>> >> +
> >>>> >> +    /* EOF considered as end of frame */
> >>>> >> +    if (buf_size == 0)
> >>>> >> +        goto flush;
> >>>> >> +
> >>>> >> +    *poutbuf      = NULL;
> >>>> >> +    *poutbuf_size = 0;
> >>>> >> +
> >>>> >> +    /* first add new buffer to parsebuffer */
> >>>> >> +    bytestream_start = av_fast_realloc(pc->buffer, &pc->buffer_size, +
> >>     pc->index + buf_size + FF_INPUT_BUFFER_PADDING_SIZE); +    if(!bytestream_start)
> >>>> >> +        goto fail;
> >>>> >> +    pc->buffer = bytestream_start;
> >>>> >> +    memcpy(&pc->buffer[pc->index], buf, buf_size);
> >>>> >
> >>>> > mandatory copying is unacceptable
> >>>> > the case where each input is exactly a png frame for example should be free of any
> >> timeconsuming operation
> >>>> >
> >>>> > maybe ff_combine_frame() would be usefull
> >>>>
> >>>> But ff_combine_frame also does memcpy, so there is no difference to my approach.
> >>>
> >>> ff_combine_frame() does not always memcpy, your code does always
> >>
> >> change my patch to only memcpy when input is not exactly a png frame.
> >>
> >> cu Peter
> 
> ping

does your code do something else than ff_combine_frame() ?
if no its duplicate code
if yes its either worse or ff_combine_frame() should be improved


[...]
-- 
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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