[FFmpeg-devel] [PATCH] Bitstream filter DTS from any format to?14bit format.

Michael Niedermayer michaelni
Thu Aug 13 23:06:22 CEST 2009


On Thu, Aug 13, 2009 at 12:38:58PM +0200, Bartlomiej Wolowiec wrote:
> Saturday 08 August 2009 03:53:11 Michael Niedermayer napisa?(a):
> > 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
> >
> >
> > [...]
> 
> Ok, I just copied it from libavcodec/dca.c.
> 
> -- 
> Bartlomiej Wolowiec

>  Changelog               |    1 
>  libavcodec/Makefile     |    1 
>  libavcodec/allcodecs.c  |    1 
>  libavcodec/dts14b_bsf.c |   64 ++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 67 insertions(+)
> 40dfc49f85a164592a81d9c68bb18b9edf692b84  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];

this size is insufficient if DCA_MAX_FRAME_SIZE is correct
see FF_INPUT_BUFFER_PADDING_SIZE

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

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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