[FFmpeg-devel] [PATCH] Bitstream filter DTS from any format to 14bit format.
Michael Niedermayer
michaelni
Sat Aug 8 03:53:11 CEST 2009
On Thu, Aug 06, 2009 at 04:43:41PM +0200, Bartlomiej Wolowiec wrote:
> Wednesday 05 August 2009 13:33:58 M?ns Rullg?rd napisa?(a):
> > Bartlomiej Wolowiec <bartek.wolowiec at gmail.com> writes:
> > > Tuesday 04 August 2009 22:29:55 M?ns Rullg?rd napisa?(a):
> > >> Bartlomiej Wolowiec <bartek.wolowiec at gmail.com> writes:
> > >> > Hi,
> > >> > Here is a small bitstream filter, which may be useful for someone.
> [...]
> > > +static int dts14b_filter(AVBitStreamFilterContext * bsfc,
> > > + AVCodecContext * avctx, const char *args,
> > > + uint8_t ** poutbuf, int *poutbuf_size,
> > > + const uint8_t * buf, int buf_size, int
> > > keyframe) +{
> > > + GetBitContext gb;
> > > + int dca_buffer_size;
> > > + uint8_t dca_buffer[DCA_MAX_FRAME_SIZE];
> > > + uint16_t *pout;
> > > +
> > > + dca_buffer_size =
> > > + ff_dca_convert_bitstream(buf, buf_size, dca_buffer,
> > > + DCA_MAX_FRAME_SIZE);
> >
> > Would it be worthwhile to check if the source is already in the
> > desired format, or shall we assume the user wouldn't ask for
> > conversion in that case?
>
> I think its unnecessary complication...
>
> > > + if (dca_buffer_size == -1) {
> > > + av_log(avctx, AV_LOG_ERROR, "Not a valid DCA frame\n");
> > > + return -1;
> > > + }
> > > +
> > > + *poutbuf_size = ((dca_buffer_size + 13) / 14) << 4;
> >
> > Shouldn't this be (((dca_buffer_size << 3) + 13) / 14) << 1, or am I
> > missing some trick?
>
> ((dca_buffer_size + 13) / 14) << 4 contains padding size
>
> > > + *poutbuf = av_malloc(*poutbuf_size + FF_INPUT_BUFFER_PADDING_SIZE);
> > > + pout = (uint16_t *) * poutbuf;
> >
> > ^
> > Please drop that space -----+ like this:
> >
> > + pout = (uint16_t *) *poutbuf
> >
> > It's not multiplication...
> >
> > > + init_get_bits(&gb, dca_buffer, dca_buffer_size);
> > > + while (get_bits_count(&gb) < dca_buffer_size << 3)
> >
> > This can over-read the end of the input buffer. You should add a few
> > bytes padding to be safe.
>
> Yes, it may over-read two bytes. I corrected it.
>
> > > + *pout++ = be2me_16(get_sbits(&gb, 14));
> > > +
> > > + while (((uint8_t *) pout - *poutbuf) & 7)
> > > + *pout++ = 0;
> >
> > Shouldn't the tail padding be included in the returned size?
>
> I hope that returning size includes tail padding ;)
>
> --
> Bartlomiej Wolowiec
> Changelog | 1
> libavcodec/Makefile | 1
> libavcodec/allcodecs.c | 1
> libavcodec/dts14b_bsf.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 67 insertions(+)
> 230ae63bdbc658d1b1a434794ce7a220f6cd9042 patch2
> Index: libavcodec/dts14b_bsf.c
> ===================================================================
> --- libavcodec/dts14b_bsf.c (wersja 0)
> +++ libavcodec/dts14b_bsf.c (wersja 0)
> @@ -0,0 +1,64 @@
> +/*
> + * DTS RAW to DTS 14B bitstream filter
> + * Copyright (c) 2009 Bartlomiej Wolowiec <bartek.wolowiec at gmail.com>
> + *
> + * 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 "avcodec.h"
> +#include "get_bits.h"
> +#include "internal.h"
> +#include "dca.h"
> +
> +static int dts14b_filter(AVBitStreamFilterContext * bsfc,
> + AVCodecContext * avctx, const char *args,
> + uint8_t ** poutbuf, int *poutbuf_size,
> + const uint8_t * buf, int buf_size, int keyframe)
> +{
> + GetBitContext gb;
> + int dca_buffer_size;
> + uint8_t dca_buffer[DCA_MAX_FRAME_SIZE+2];
> + uint16_t *pout;
> +
> + dca_buffer_size =
> + ff_dca_convert_bitstream(buf, buf_size, dca_buffer,
> + DCA_MAX_FRAME_SIZE);
> + if (dca_buffer_size == -1) {
can i convince you to treat all negative values as error?
its more consistent through ffmpeg and allows functions return more
verbose error codes
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
In a rich man's house there is no place to spit but his face.
-- Diogenes of Sinope
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