[FFmpeg-devel] [PATCH] libavdevice: JACK demuxer

[Michael Niedermayer]

On Fri, Mar 13, 2009 at 09:05:38PM +0100, Olivier Guilyardi wrote:
> Attached: jack demuxer 0.10
> 
> Michael Niedermayer wrote:
> 
> > also, it seems libavutil/fifo.c/h could be used now (as ive fixed a
> > alignment bug) so you dont have to implement anything, just call the
> > code from fifo.*
> 
> Done
> 
> Changes since 0.9:
> - use libavutil fifo instead of jack ringbuffer
> - increase fifo buffers size from 4 to 16 audio packets
> - less paranoid protection against underrun
> - fix dependency on timefilter (in libavformat/Makefile)
> - rename PrivateData to JackData for consistency with other demuxers
> 
> --
>   Olivier

[...]
> Index: libavdevice/jack_audio.c
> ===================================================================
> --- libavdevice/jack_audio.c	(revision 0)
> +++ libavdevice/jack_audio.c	(revision 0)
[...]
> +#include "config.h"
> +#include <semaphore.h>
> +#include <jack/jack.h>
> +
> +#include "libavutil/log.h"
> +#include "libavutil/fifo.h"
> +#include "libavcodec/avcodec.h"
> +#include "libavformat/avformat.h"
> +#include "libavformat/timefilter.h"
> +
> +/**
> + * Size of the internal fifo buffers as a number of audio packets
> + */
> +#define FIFO_PACKETS_NUM 16
> +

> +#define FIFO_WRITE_SPACE(fifo) (fifo->end - fifo->buffer - av_fifo_size(fifo))

i would prefer if you did not use end/buffer directly but kept a private
variable that is the size


[...]
> +        if (av_new_packet(&pkt, pkt_size) < 0) {
> +            av_log(context, AV_LOG_ERROR, "Could not create packet of size %d\n", pkt_size);
> +            return AVERROR(EIO);
> +        }
> +        av_fifo_generic_write(self->new_pkt_fifo, &pkt, sizeof(pkt), NULL);

it should be possible to use the function ptr argument of
av_fifo_generic_write to avoid the copy


[...]
> +static int audio_read_packet(AVFormatContext *context, AVPacket *pkt)
> +{
> +    JackData *self = context->priv_data;
> +    struct timespec timeout = {0, 0};
> +    int test;
> +
> +    /* Activate the jack client on first packet read. Activating the JACK client
> +     * means that process_callback() starts to get called at regular interval.
> +     * If we activate it in audio_read_header(), we're actually reading audio data
> +     * from the device before instructed to, and that may result in an overrun. */
> +    if (!self->activated && activate_jack(self, context))
> +        return AVERROR(EIO);

i still think this belongs in audio_read_header()


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

Into a blind darkness they enter who follow after the Ignorance,
they as if into a greater darkness enter who devote themselves
to the Knowledge alone. -- Isha Upanishad
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