[FFmpeg-devel] [PATCH 2/3] lavfi: add a generic API for buffer queues.

[Michael Niedermayer]

On Fri, Apr 27, 2012 at 05:38:41PM +0200, Nicolas George wrote:
> 
> Signed-off-by: Nicolas George <nicolas.george at normalesup.org>
> ---
>  libavfilter/bufferqueue.h |   73 +++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 73 insertions(+), 0 deletions(-)
>  create mode 100644 libavfilter/bufferqueue.h
> 
> diff --git a/libavfilter/bufferqueue.h b/libavfilter/bufferqueue.h
> new file mode 100644
> index 0000000..6ad00ee
> --- /dev/null
> +++ b/libavfilter/bufferqueue.h
> @@ -0,0 +1,73 @@
> +/*
> + * Generic buffer queue
> + * Copyright (c) 2012 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
> + */
> +
> +#ifndef AVFILTER_BUFFERQUEUE_H
> +#define AVFILTER_BUFFERQUEUE_H
> +
> +#ifndef FF_BUFQUEUE_SIZE
> +#define FF_BUFQUEUE_SIZE 32
> +#endif
> +
> +#include "avfilter.h"
> +#include "libavutil/avassert.h"
> +
> +struct ff_bufqueue {
> +    AVFilterBufferRef *queue[FF_BUFQUEUE_SIZE];
> +    unsigned short head;
> +    unsigned short available;
> +};
> +
> +#define BUCKET(i) queue->queue[(queue->head + (i)) % FF_BUFQUEUE_SIZE]

i suggest & (FF_BUFQUEUE_SIZE-1) and only allowing powers of 2
the & should be much faster than a %


> +
> +static inline void ff_bufqueue_add(void *log, struct ff_bufqueue *queue,
> +                                   AVFilterBufferRef *buf)
> +{
> +    if (queue->available == FF_BUFQUEUE_SIZE) {
> +        av_log(log, AV_LOG_WARNING, "Buffer queue overflow, dropping.\n");
> +        avfilter_unref_buffer(BUCKET(--queue->available));
> +    }
> +    BUCKET(queue->available++) = buf;
> +}
> +
> +static inline AVFilterBufferRef *ff_bufqueue_get(struct ff_bufqueue *queue,
> +                                                 unsigned index)
> +{
> +    return index < queue->available ? BUCKET(index) : NULL;
> +}
> +
> +static inline AVFilterBufferRef *ff_bufqueue_take(struct ff_bufqueue *queue)
> +{
> +    AVFilterBufferRef *ret = queue->queue[queue->head];
> +    queue->available--;

a av_assert() could be used here to detect tries to take out of an
empty queue

otherwise LGTM as long as theres no plan to use this between 2 threads


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

What does censorship reveal? It reveals fear. -- Julian Assange
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