Re: [PATCH v2 09/17] audio/mixeng: calculate number of input frames

[Marc-André Lureau]

Hi

On Mon, Feb 6, 2023 at 10:52 PM Volker Rümelin <vr_qemu@t-online.de> wrote:
>
> Calculate the exact number of audio input frames needed to get
> a given number of audio output frames. The exact number of
> frames depends only on the difference of opos - ipos and the
> number of output frames. When downsampling, this function
> returns the maximum number of input frames needed.
>
> This function will later replace the audio_frontend_frames_out()
> function, which calculates the average number of input frames
> rounded down to the nearest integer.
>
> Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>

We usually introduce functions with their usage, but ok
Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>



> ---
>  audio/mixeng.c | 36 ++++++++++++++++++++++++++++++++++++
>  audio/mixeng.h |  1 +
>  2 files changed, 37 insertions(+)
>
> diff --git a/audio/mixeng.c b/audio/mixeng.c
> index fe454e0725..6bb3d54f77 100644
> --- a/audio/mixeng.c
> +++ b/audio/mixeng.c
> @@ -440,6 +440,42 @@ void st_rate_stop (void *opaque)
>      g_free (opaque);
>  }
>
> +/**
> + * st_rate_frames_in() - returns the number of frames needed to
> + * get frames_out frames after resampling
> + *
> + * @opaque: pointer to struct rate
> + * @frames_out: number of frames
> + */
> +uint32_t st_rate_frames_in(void *opaque, uint32_t frames_out)
> +{
> +    struct rate *rate = opaque;
> +    uint64_t opos_start, opos_end;
> +    uint32_t ipos_start, ipos_end;
> +
> +    if (rate->opos_inc == 1ULL << 32) {
> +        return frames_out;
> +    }
> +
> +    if (frames_out) {
> +        opos_start = rate->opos;
> +        ipos_start = rate->ipos;
> +    } else {
> +        uint64_t offset;
> +
> +        /* add offset = ceil(opos_inc) to opos and ipos to avoid an 
> underflow */
> +        offset = (rate->opos_inc + (1ULL << 32) - 1) & ~((1ULL << 32) - 1);
> +        opos_start = rate->opos + offset;
> +        ipos_start = rate->ipos + (offset >> 32);
> +    }
> +    /* last frame written was at opos_start - rate->opos_inc */
> +    opos_end = opos_start - rate->opos_inc + rate->opos_inc * frames_out;
> +    ipos_end = (opos_end >> 32) + 1;
> +
> +    /* last frame read was at ipos_start - 1 */
> +    return ipos_end + 1 > ipos_start ? ipos_end + 1 - ipos_start : 0;
> +}
> +
>  void mixeng_clear (struct st_sample *buf, int len)
>  {
>      memset (buf, 0, len * sizeof (struct st_sample));
> diff --git a/audio/mixeng.h b/audio/mixeng.h
> index 2dcd6df245..64c1e231cc 100644
> --- a/audio/mixeng.h
> +++ b/audio/mixeng.h
> @@ -52,6 +52,7 @@ void st_rate_flow(void *opaque, st_sample *ibuf, st_sample 
> *obuf,
>  void st_rate_flow_mix(void *opaque, st_sample *ibuf, st_sample *obuf,
>                        size_t *isamp, size_t *osamp);
>  void st_rate_stop (void *opaque);
> +uint32_t st_rate_frames_in(void *opaque, uint32_t frames_out);
>  void mixeng_clear (struct st_sample *buf, int len);
>  void mixeng_volume (struct st_sample *buf, int len, struct mixeng_volume 
> *vol);
>
> --
> 2.35.3
>


--
Marc-André Lureau