[FFmpeg-devel] [PATCH] Add af_afifo - audio fifo filter

[Stefano Sabatini]

On date Tuesday 2010-08-17 19:44:31 -0700, S.N. Hemanth Meenakshisundaram encoded:
> Added filter.texi doc
> 
> ---
>  doc/filters.texi         |    8 +++
>  libavfilter/Makefile     |    1 +
>  libavfilter/af_afifo.c   |  118 ++++++++++++++++++++++++++++++++++++++++++++++
>  libavfilter/allfilters.c |    1 +
>  4 files changed, 128 insertions(+), 0 deletions(-)
>  create mode 100644 libavfilter/af_afifo.c
> 
> 
> 

> diff --git a/doc/filters.texi b/doc/filters.texi
> index ff77fc4..f72f54e 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -8,6 +8,14 @@ build.
>  
>  Below is a description of the currently available video filters.
>  
> + at section afifo
> +
> +First in first out buffer for audio frames.
> +
> + at example
> +./ffmpeg -i in.wav -af "afifo" out.wav
> + at end example

Please be more informative here. Check the docs I wrote for the
pending video fifo filter patch (I'm still fixing some bugs on it).

Also maybe we should start to write some tests for audio.

> +
>  @section crop
>  
>  Crop the input video to @var{x}:@var{y}:@var{width}:@var{height}.
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 3e25e39..0e38e8a 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -14,6 +14,7 @@ OBJS = allfilters.o                                                     \
>         graphparser.o                                                    \
>         parseutils.o                                                     \
>  
> +OBJS-$(CONFIG_AFIFO_FILTER)                  += af_afifo.o
>  OBJS-$(CONFIG_NULLAUD_FILTER)                += af_nullaud.o
>  
>  OBJS-$(CONFIG_ASPECT_FILTER)                 += vf_aspect.o
> diff --git a/libavfilter/af_afifo.c b/libavfilter/af_afifo.c
> new file mode 100644
> index 0000000..33ce8e0
> --- /dev/null
> +++ b/libavfilter/af_afifo.c
> @@ -0,0 +1,118 @@
> +/*
> + * audio frame FIFO
> + * copyright (c) 2010 S.N. Hemanth Meenakshisundaram
> + *
> + * 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 "avfilter.h"
> +
> +typedef struct BufSamples
> +{

Nit: "{" on the same line, same below.

> +    AVFilterBufferRef *samples;

samplesref is less ambiguous.

> +    struct BufSamples  *next;
> +} BufSamples;
> +
> +typedef struct
> +{
> +    BufSamples  root;          ///< first buffered audio buffer.
> +    BufSamples *last;          ///< last buffered audio buffer.
> +    int frame_requests_pending; ///< flag to indicate pending frame requests.
> +} FifoContext;
> +
> +static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
> +{
> +    FifoContext *fifo = ctx->priv;
> +    fifo->last = &fifo->root;
> +
> +    return 0;
> +}
> +
> +static av_cold void uninit(AVFilterContext *ctx)
> +{
> +    FifoContext *fifo = ctx->priv;
> +    BufSamples *samples, *tmp;
> +
> +    for(samples = fifo->root.next; samples; samples = tmp) {
> +        tmp = samples->next;
> +        avfilter_unref_buffer(samples->samples);
> +        av_free(samples);
> +    }
> +}
> +
> +static void filter_samples(AVFilterLink *link, AVFilterBufferRef *samplesref)
> +{
> +    FifoContext *fifo = link->dst->priv;
> +
> +    // if frame requests are pending, directly pass on buffer, do not queue.
> +    if (fifo->frame_requests_pending) {
> +        filter_samples(link->dst->outputs[0], samplesref);
> +        fifo->frame_requests_pending--;
> +        return;
> +    }
> +    fifo->last->next = av_mallocz(sizeof(BufSamples));
> +    fifo->last = fifo->last->next;
> +    fifo->last->samples = samplesref;
> +}
> +
> +static int request_frame(AVFilterLink *link)
> +{
> +    FifoContext *fifo = link->src->priv;
> +    BufSamples *tmp;
> +
> +    if(!fifo->root.next)

Nits: if_(, same below.

> +        if(avfilter_request_frame(link->src->inputs[0])) {
> +            fifo->frame_requests_pending++;
> +            return -1;

Propagate the avfilter_request_frame error code.

> +        }
> +
> +    /**
> +     * by passing our own reference, we give ownership of the reference to the
> +     * next filter so we don't have to worry about dereferencing it ourselves.
> +     */
> +    avfilter_filter_samples(link, fifo->root.next->samples);
> +
> +    if(fifo->last == fifo->root.next)
> +        fifo->last = &fifo->root;
> +    tmp = fifo->root.next->next;
> +    av_free(fifo->root.next);
> +    fifo->root.next = tmp;
> +
> +    return 0;
> +}
> +

> +AVFilter avfilter_af_afifo =
> +{

"{" on the same line.

> +    .name      = "afifo",

Missing description.

> +
> +    .init      = init,
> +    .uninit    = uninit,
> +
> +    .priv_size = sizeof(FifoContext),
> +
> +    .inputs    = (AVFilterPad[]) {{ .name             = "default",
> +                                    .type             = AVMEDIA_TYPE_AUDIO,
> +                                    .get_audio_buffer = avfilter_null_get_audio_buffer,
> +                                    .filter_samples   = filter_samples,
> +                                    .rej_perms        = AV_PERM_REUSE2, },
> +                                  { .name = NULL}},
> +    .outputs   = (AVFilterPad[]) {{ .name             = "default",
> +                                    .type             = AVMEDIA_TYPE_AUDIO,
> +                                    .request_frame    = request_frame, },
> +                                  { .name = NULL}},
> +};
> +
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index cab7d4b..9bf8c10 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -34,6 +34,7 @@ void avfilter_register_all(void)
>          return;
>      initialized = 1;
>  
> +    REGISTER_FILTER (AFIFO,       afifo,       af);
>      REGISTER_FILTER (NULLAUD,     nullaud,     af);
>  
>      REGISTER_FILTER (ASPECT,      aspect,      vf);
> 

Regards.
-- 
FFmpeg = Fiendish & Furious Martial Portable Educated Gargoyle