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audio: make recording packet length calculation exact

Browse source 
Introduce the new function st_rate_frames_out() to calculate the
exact number of audio output frames the resampling code can
generate from a given number of audio input frames. When upsampling,
this function returns the maximum number of output frames.

This new function replaces the audio_frontend_frames_in()
function, which calculated the average number of output frames
rounded down to the nearest integer. The audio_frontend_frames_in()
function was additionally used to limit the number of output frames
to the resample buffer size. In audio_pcm_sw_read() the variable
resample_buf.size replaces the open coded audio_frontend_frames_in()
function. In audio_run_in() an additional MIN() function is
necessary.

After this patch the audio packet length calculation for audio
recording is exact.

Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20230224190555.7409-12-vr_qemu@t-online.de>
This commit is contained in:
Volker Rümelin 2023-02-24 20:05:52 +01:00 • committed by Marc-André Lureau
parent fbde1edf06
commit a9ea567873
3 changed files with 50 additions and 21 deletions
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41
audio/mixeng.c
View file

@ -440,6 +440,47 @@ void st_rate_stop (void *opaque)
g_free (opaque);
}
/**
* st_rate_frames_out() - returns the number of frames the resampling code
* generates from frames_in frames
*
* @opaque: pointer to struct rate
* @frames_in: number of frames
*
* When upsampling, there may be more than one correct result. In this case,
* the function returns the maximum number of output frames the resampling
* code can generate.
*/
uint32_t st_rate_frames_out(void *opaque, uint32_t frames_in)
{
struct rate *rate = opaque;
uint64_t opos_end, opos_delta;
uint32_t ipos_end;
uint32_t frames_out;
if (rate->opos_inc == 1ULL << 32) {
return frames_in;
}
/* no output frame without at least one input frame */
if (!frames_in) {
return 0;
}
/* last frame read was at rate->ipos - 1 */
ipos_end = rate->ipos - 1 + frames_in;
opos_end = (uint64_t)ipos_end << 32;
/* last frame written was at rate->opos - rate->opos_inc */
if (opos_end + rate->opos_inc <= rate->opos) {
return 0;
}
opos_delta = opos_end - rate->opos + rate->opos_inc;
frames_out = opos_delta / rate->opos_inc;
return opos_delta % rate->opos_inc ? frames_out : frames_out - 1;
}
/**
* st_rate_frames_in() - returns the number of frames needed to
* get frames_out frames after resampling