Re: [PATCH v2 17/17] audio: remove sw->ratio

[Marc-André Lureau]

On Mon, Feb 6, 2023 at 10:53 PM Volker Rümelin <vr_qemu@t-online.de> wrote:
>
> Simplify the resample buffer size calculation.
>
> For audio playback we have
> sw->ratio = ((int64_t)sw->hw->info.freq << 32) / sw->info.freq;
> samples = ((int64_t)sw->HWBUF.size << 32) / sw->ratio;
>
> This can be simplified to
> samples = muldiv64(sw->HWBUF.size, sw->info.freq, sw->hw->info.freq);
>
> For audio recording we have
> sw->ratio = ((int64_t)sw->info.freq << 32) / sw->hw->info.freq;
> samples = (int64_t)sw->HWBUF.size * sw->ratio >> 32;
>
> This can be simplified to
> samples = muldiv64(sw->HWBUF.size, sw->info.freq, sw->hw->info.freq);
>
> With hw = sw->hw this becomes in both cases
> samples = muldiv64(HWBUF.size, sw->info.freq, hw->info.freq);
>
> Now that sw->ratio is no longer needed, remove sw->ratio.
>
> Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>



> ---
>  audio/audio.c          |  1 -
>  audio/audio_int.h      |  2 --
>  audio/audio_template.h | 30 +++++++++---------------------
>  3 files changed, 9 insertions(+), 24 deletions(-)
>
> diff --git a/audio/audio.c b/audio/audio.c
> index 4836ab8ca8..70b096713c 100644
> --- a/audio/audio.c
> +++ b/audio/audio.c
> @@ -478,7 +478,6 @@ static int audio_attach_capture (HWVoiceOut *hw)
>          sw->info = hw->info;
>          sw->empty = 1;
>          sw->active = hw->enabled;
> -        sw->ratio = ((int64_t) hw_cap->info.freq << 32) / sw->info.freq;
>          sw->vol = nominal_volume;
>          sw->rate = st_rate_start (sw->info.freq, hw_cap->info.freq);
>          QLIST_INSERT_HEAD (&hw_cap->sw_head, sw, entries);
> diff --git a/audio/audio_int.h b/audio/audio_int.h
> index 8b163e1759..d51d63f08d 100644
> --- a/audio/audio_int.h
> +++ b/audio/audio_int.h
> @@ -108,7 +108,6 @@ struct SWVoiceOut {
>      AudioState *s;
>      struct audio_pcm_info info;
>      t_sample *conv;
> -    int64_t ratio;
>      STSampleBuffer resample_buf;
>      void *rate;
>      size_t total_hw_samples_mixed;
> @@ -126,7 +125,6 @@ struct SWVoiceIn {
>      AudioState *s;
>      int active;
>      struct audio_pcm_info info;
> -    int64_t ratio;
>      void *rate;
>      size_t total_hw_samples_acquired;
>      STSampleBuffer resample_buf;
> diff --git a/audio/audio_template.h b/audio/audio_template.h
> index 7e116426c7..e42326c20d 100644
> --- a/audio/audio_template.h
> +++ b/audio/audio_template.h
> @@ -108,32 +108,23 @@ static void glue (audio_pcm_sw_free_resources_, TYPE) 
> (SW *sw)
>  static int glue (audio_pcm_sw_alloc_resources_, TYPE) (SW *sw)
>  {
>      HW *hw = sw->hw;
> -    int samples;
> +    uint64_t samples;
>
>      if (!glue(audio_get_pdo_, TYPE)(sw->s->dev)->mixing_engine) {
>          return 0;
>      }
>
> -#ifdef DAC
> -    samples = ((int64_t)sw->HWBUF.size << 32) / sw->ratio;
> -#else
> -    samples = (int64_t)sw->HWBUF.size * sw->ratio >> 32;
> -#endif
> -    if (audio_bug(__func__, samples < 0)) {
> -        dolog("Can not allocate buffer for `%s' (%d samples)\n",
> -              SW_NAME(sw), samples);
> -        return -1;
> -    }
> -
> +    samples = muldiv64(HWBUF.size, sw->info.freq, hw->info.freq);
>      if (samples == 0) {
> -        size_t f_fe_min;
> +        uint64_t f_fe_min;
> +        uint64_t f_be = (uint32_t)hw->info.freq;
>
>          /* f_fe_min = ceil(1 [frames] * f_be [Hz] / size_be [frames]) */
> -        f_fe_min = (hw->info.freq + HWBUF.size - 1) / HWBUF.size;
> +        f_fe_min = (f_be + HWBUF.size - 1) / HWBUF.size;
>          qemu_log_mask(LOG_UNIMP,
>                        AUDIO_CAP ": The guest selected a " NAME " sample rate"
> -                      " of %d Hz for %s. Only sample rates >= %zu Hz are"
> -                      " supported.\n",
> +                      " of %d Hz for %s. Only sample rates >= %" PRIu64 " Hz"
> +                      " are supported.\n",
>                        sw->info.freq, sw->name, f_fe_min);
>          return -1;
>      }
> @@ -141,9 +132,9 @@ static int glue (audio_pcm_sw_alloc_resources_, TYPE) (SW 
> *sw)
>      /*
>       * Allocate one additional audio frame that is needed for upsampling
>       * if the resample buffer size is small. For large buffer sizes take
> -     * care of overflows.
> +     * care of overflows and truncation.
>       */
> -    samples = samples < INT_MAX ? samples + 1 : INT_MAX;
> +    samples = samples < SIZE_MAX ? samples + 1 : SIZE_MAX;
>      sw->resample_buf.buffer = g_new0(st_sample, samples);
>      sw->resample_buf.size = samples;
>      sw->resample_buf.pos = 0;
> @@ -170,11 +161,8 @@ static int glue (audio_pcm_sw_init_, TYPE) (
>      sw->hw = hw;
>      sw->active = 0;
>  #ifdef DAC
> -    sw->ratio = ((int64_t) sw->hw->info.freq << 32) / sw->info.freq;
>      sw->total_hw_samples_mixed = 0;
>      sw->empty = 1;
> -#else
> -    sw->ratio = ((int64_t) sw->info.freq << 32) / sw->hw->info.freq;
>  #endif
>
>      if (sw->info.is_float) {
> --
> 2.35.3
>


--
Marc-André Lureau