[pulseaudio-discuss] [PATCH] sink, source: Add a mode to avoid resampling if possible

[Tanu Kaskinen]

On Sat, 2017-01-28 at 13:26 +0530, Arun Raghavan wrote:
> This adds an "avoid-resampling" option to daemon.conf that makes the
> daemon try to use the stream sample rate if possible (the device needs
> to support it, which currently only ALSA does), and there should not be
> any other stream connected).
> 
> This should enable some of the "audiophile" use-cases where users wish
> to play high sample rate audio files without resampling.
> 
> We still will do conversion, though which means that the 96/24 case will
> require that the default format be set to be 24-bit as well, this will
> force all streams to be upconverted, which other than the wasted
> resources should be relatively harmless.

That last paragraph isn't entirely coherent. Feel free to copy-paste
this:

Audiophiles who demand "no modification of audio", please note:
avoiding sample rate coversion doesn't necessarily mean that we don't
have to do any conversion. We don't reconfigure the sink/source sample
format dynamically based on the stream format, so if there are
mismatches between the device and stream sample formats (e.g. 16-bit
vs. 24-bit), then the samples have to be converted.

> @@ -1442,7 +1443,12 @@ int pa_sink_update_rate(pa_sink *s, uint32_t rate, bool passthrough) {
>      if (PA_UNLIKELY(!pa_sample_rate_valid(desired_rate)))
>          return -1;
>  
> -    if (!passthrough && default_rate != desired_rate && alternate_rate != desired_rate) {
> +    if (avoid_resampling) {
> +        /* We just try to set the sink input's sample rate if it's not too low */
> +        if (rate > default_rate || rate > alternate_rate)
> +            desired_rate = rate;

This doesn't work. desired_rate is already set to rate, so this does
nothing.

-- 
Tanu

https://www.patreon.com/tanuk