[pulseaudio-discuss] [PATCH v3] pacat: Write to stream only in frame-sized chunks

Tanu Kaskinen tanuk at iki.fi
Tue Dec 20 18:04:57 UTC 2016

On Tue, 2016-12-20 at 09:07 +0000, Ahmed S. Darwish wrote:
> Current pacat code reads whatever available from STDIN and writes
> it directly to the playback stream. A minimal buffer is created
> for each read operation; no further reads are then allowed unless
> earlier read buffer has been fully consumed by a stream write.
> While quite simple, this model breaks upon the new requirements of
> writing only frame-aligned data to the stream (commits #1 and #2).
> The kernel read syscall can return a length much smaller than the
> frame-aligned size requested, leading to invalid unaligned writes.
> This can easily be reproduced by choosing a starved STDIN backend:
>   pacat /dev/random    pa_stream_write() failed: EINVAL
>   echo 1234 | pacat    pa_stream_write() failed: EINVAL
> or by playing an incomplete WAV file in raw, non-paplay, mode.
> So guard against such incomplete kernel reads by writing only in
> frame-aligned sizes, while caching any trailing partial frame for
> subsequent writes.
> Other operation modes are not affected. Non-raw paplay playback is
> handled by libsndfile, ensuring complete reads, and recording mode
> just writes to the STDOUT fd without any special needs.
> CommitReference: 22827a5e1e62
> CommitReference: 150ace90f380
> BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=98475
> BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=77595
> Suggested-by: David Henningsson <diwic at ubuntu.com>
> Signed-off-by: Ahmed S. Darwish <darwish.07 at gmail.com>
> ---
>  src/utils/pacat.c | 98 ++++++++++++++++++++++++++++++-------------------------
>  1 file changed, 53 insertions(+), 45 deletions(-)

Thanks! Applied.



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