[pulseaudio-discuss] [PATCH RFCv3 48/51] alsa-sink: Assume left_to_play can be computed, save one call to snd_pcm_avail()

[Alexander E. Patrakov]

05.11.2014 04:26, Peter Meerwald wrote:
> From: Peter Meerwald <p.meerwald at bct-electronic.com>
>
> after a completed write in mmap_write(), compute the new left_to_play instead
> of asking ALSA what the new value would be

Hi.

Would it be possible (in a debugging patch not meant to be merged) to 
save the computed left_to_play value in a different variable and log 
both expected and actual values?

>
> Signed-off-by: Peter Meerwald <pmeerw at pmeerw.net>
> ---
>   src/modules/alsa/alsa-sink.c | 20 +++++++++++++++-----
>   1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/src/modules/alsa/alsa-sink.c b/src/modules/alsa/alsa-sink.c
> index 3690d8d..0d13716 100644
> --- a/src/modules/alsa/alsa-sink.c
> +++ b/src/modules/alsa/alsa-sink.c
> @@ -512,13 +512,16 @@ static int mmap_write(struct userdata *u, pa_usec_t *sleep_usec, bool polled, bo
>       bool work_done = false;
>       pa_usec_t max_sleep_usec = 0, process_usec = 0;
>       size_t left_to_play, input_underrun;
> +    size_t sleep_bytes = 0;
>       unsigned j = 0;
>
>       pa_assert(u);
>       pa_sink_assert_ref(u->sink);
>
> -    if (u->use_tsched)
> +    if (u->use_tsched) {
>           hw_sleep_time(u, &max_sleep_usec, &process_usec);
> +        sleep_bytes = PA_USEC_TO_BYTES(process_usec + max_sleep_usec/2, &u->sink->sample_spec);
> +    }
>
>       for (;;) {
>           snd_pcm_sframes_t n;
> @@ -554,8 +557,7 @@ static int mmap_write(struct userdata *u, pa_usec_t *sleep_usec, bool polled, bo
>               * need to guarantee that clients only have to keep around
>               * a single hw buffer length. */
>
> -            if (!polled &&
> -                PA_BYTES_TO_USEC(left_to_play, &u->sink->sample_spec) > process_usec+max_sleep_usec/2) {
> +            if (!polled && left_to_play > sleep_bytes) {
>   #ifdef DEBUG_TIMING
>                   pa_log_debug("Not filling up, because too early.");
>   #endif
> @@ -666,13 +668,21 @@ static int mmap_write(struct userdata *u, pa_usec_t *sleep_usec, bool polled, bo
>               pa_log_debug("Wrote %lu bytes (of possible %lu bytes)", (unsigned long) written, (unsigned long) n_bytes);
>   #endif
>
> -            if (written >= n_bytes)
> -                break;
> +            if (written >= n_bytes) {
> +                if (u->use_tsched &&
> +                    sframes * u->frame_size == n_bytes &&
> +                    left_to_play + n_bytes > sleep_bytes) {
> +                    left_to_play += n_bytes;
> +                    goto done;
> +                } else
> +                    break;
> +            }
>
>               n_bytes -= written;
>           }
>       }
>
> +done:
>       input_underrun = pa_sink_process_input_underruns(u->sink, left_to_play);
>
>       if (u->use_tsched) {
>


-- 
Alexander E. Patrakov