From 6d206a7b28ebf6eb5ad67aeef51b3de92145b994 Mon Sep 17 00:00:00 2001 From: "Ryan C. Gordon" Date: Fri, 22 Sep 2017 07:42:24 -0400 Subject: [PATCH] audio: Stream resampling now saves some samples from previous run for padding. Previously, the padding was silence, which was a problem when streaming since you would sample a little bit of this silence between each buffer. We still need a means to get padding data for the right hand side, but this patch makes the resampler output more correct. --- src/audio/SDL_audiocvt.c | 76 +++++++++++++++++++++++----------------- 1 file changed, 43 insertions(+), 33 deletions(-) diff --git a/src/audio/SDL_audiocvt.c b/src/audio/SDL_audiocvt.c index b25483a22..7c977e6c0 100644 --- a/src/audio/SDL_audiocvt.c +++ b/src/audio/SDL_audiocvt.c @@ -464,15 +464,21 @@ SDL_FreeResampleFilter(void) ResamplerFilterDifference = NULL; } +static int +ResamplerPadding(const int inrate, const int outrate) +{ + return (inrate > outrate) ? (int) SDL_ceil(((float) (RESAMPLER_SAMPLES_PER_ZERO_CROSSING * inrate) / ((float) outrate))) : RESAMPLER_SAMPLES_PER_ZERO_CROSSING; +} +/* lpadding and rpadding are expected to be buffers of (ResamplePadding(inrate, outrate) * chans * sizeof (float)) bytes. */ static int SDL_ResampleAudio(const int chans, const int inrate, const int outrate, - float *last_sample, const float *inbuf, + float *lpadding, float *rpadding, const float *inbuf, const int inbuflen, float *outbuf, const int outbuflen) { const float outtimeincr = 1.0f / ((float) outrate); const float ratio = ((float) outrate) / ((float) inrate); - /*const int padding_len = (ratio < 1.0f) ? (int) SDL_ceilf(((float) (RESAMPLER_SAMPLES_PER_ZERO_CROSSING * inrate) / ((float) outrate))) : RESAMPLER_SAMPLES_PER_ZERO_CROSSING;*/ + const int paddinglen = ResamplerPadding(inrate, outrate); const int framelen = chans * (int)sizeof (float); const int inframes = inbuflen / framelen; const int wantedoutframes = (int) ((inbuflen / framelen) * ratio); /* outbuflen isn't total to write, it's total available. */ @@ -499,16 +505,16 @@ SDL_ResampleAudio(const int chans, const int inrate, const int outrate, /* do this twice to calculate the sample, once for the "left wing" and then same for the right. */ /* !!! FIXME: do both wings in one loop */ for (j = 0; (filterindex1 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)) < RESAMPLER_FILTER_SIZE; j++) { - /* !!! FIXME: insample uses zero for padding samples, but it should use prior state from last_sample. */ const int srcframe = srcindex - j; - const float insample = (srcframe < 0) ? 0.0f : inbuf[(srcframe * chans) + chan]; /* !!! FIXME: we can bubble this conditional out of here by doing a pre loop. */ + /* !!! FIXME: we can bubble this conditional out of here by doing a pre loop. */ + const float insample = (srcframe < 0) ? lpadding[((paddinglen + srcframe) * chans) + chan] : inbuf[(srcframe * chans) + chan]; outsample += (insample * (ResamplerFilter[filterindex1 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)] + (interpolation1 * ResamplerFilterDifference[filterindex1 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)]))); } for (j = 0; (filterindex2 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)) < RESAMPLER_FILTER_SIZE; j++) { const int srcframe = srcindex + 1 + j; - /* !!! FIXME: insample uses zero for padding samples, but it should use prior state from last_sample. */ - const float insample = (srcframe >= inframes) ? 0.0f : inbuf[(srcframe * chans) + chan]; /* !!! FIXME: we can bubble this conditional out of here by doing a post loop. */ + /* !!! FIXME: we can bubble this conditional out of here by doing a post loop. */ + const float insample = (srcframe >= inframes) ? rpadding[((srcframe - inframes) * chans) + chan] : inbuf[(srcframe * chans) + chan]; outsample += (insample * (ResamplerFilter[filterindex2 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)] + (interpolation2 * ResamplerFilterDifference[filterindex2 + (j * RESAMPLER_SAMPLES_PER_ZERO_CROSSING)]))); } *(dst++) = outsample; @@ -693,8 +699,8 @@ SDL_ResampleCVT(SDL_AudioCVT *cvt, const int chans, const SDL_AudioFormat format /* !!! FIXME in 2.1: there are ten slots in the filter list, and the theoretical maximum we use is six (seven with NULL terminator). !!! FIXME in 2.1: We need to store data for this resampler, because the cvt structure doesn't store the original sample rates, !!! FIXME in 2.1: so we steal the ninth and tenth slot. :( */ - const int srcrate = (int) (size_t) cvt->filters[SDL_AUDIOCVT_MAX_FILTERS-1]; - const int dstrate = (int) (size_t) cvt->filters[SDL_AUDIOCVT_MAX_FILTERS]; + const int inrate = (int) (size_t) cvt->filters[SDL_AUDIOCVT_MAX_FILTERS-1]; + const int outrate = (int) (size_t) cvt->filters[SDL_AUDIOCVT_MAX_FILTERS]; const float *src = (const float *) cvt->buf; const int srclen = cvt->len_cvt; /*float *dst = (float *) cvt->buf; @@ -702,13 +708,15 @@ SDL_ResampleCVT(SDL_AudioCVT *cvt, const int chans, const SDL_AudioFormat format /* !!! FIXME: remove this if we can get the resampler to work in-place again. */ float *dst = (float *) (cvt->buf + srclen); const int dstlen = (cvt->len * cvt->len_mult) - srclen; - float state[8]; + const int paddingsamples = (ResamplerPadding(inrate, outrate) * chans); + float *padding = SDL_stack_alloc(float, paddingsamples); SDL_assert(format == AUDIO_F32SYS); - SDL_zero(state); + /* we keep no streaming state here, so pad with silence on both ends. */ + SDL_memset(padding, '\0', paddingsamples * sizeof (float)); - cvt->len_cvt = SDL_ResampleAudio(chans, srcrate, dstrate, state, src, srclen, dst, dstlen); + cvt->len_cvt = SDL_ResampleAudio(chans, inrate, outrate, padding, padding, src, srclen, dst, dstlen); SDL_memcpy(cvt->buf, dst, cvt->len_cvt); /* !!! FIXME: remove this if we can get the resampler to work in-place again. */ @@ -1195,25 +1203,19 @@ SetupLibSampleRateResampling(SDL_AudioStream *stream) #endif /* HAVE_LIBSAMPLERATE_H */ -typedef struct -{ - SDL_bool resampler_seeded; - union - { - float f[8]; - Sint16 si16[2]; - } resampler_state; -} SDL_AudioStreamResamplerState; - static int SDL_ResampleAudioStream(SDL_AudioStream *stream, const void *_inbuf, const int inbuflen, void *_outbuf, const int outbuflen) { const float *inbuf = (const float *) _inbuf; float *outbuf = (float *) _outbuf; - SDL_AudioStreamResamplerState *state = (SDL_AudioStreamResamplerState*)stream->resampler_state; - const int chans = (int)stream->pre_resample_channels; - - SDL_assert(chans <= SDL_arraysize(state->resampler_state.f)); + const int chans = (int) stream->pre_resample_channels; + const int inrate = stream->src_rate; + const int outrate = stream->dst_rate; + const int paddingsamples = ResamplerPadding(inrate, outrate) * chans; + const int paddingbytes = paddingsamples * sizeof (float); + float *lpadding = (float *) stream->resampler_state; + float *rpadding = SDL_stack_alloc(float, paddingsamples); + int retval; if (inbuf == ((const float *) outbuf)) { /* !!! FIXME can't work in-place (for now!). */ Uint8 *ptr = EnsureStreamBufferSize(stream, inbuflen + outbuflen); @@ -1226,19 +1228,25 @@ SDL_ResampleAudioStream(SDL_AudioStream *stream, const void *_inbuf, const int i outbuf = (float *) ptr; } - if (!state->resampler_seeded) { - SDL_zero(state->resampler_state.f); - state->resampler_seeded = SDL_TRUE; - } + /* !!! FIXME: streaming current resamples on Put, because of probably good reasons I can't remember right now, but if we resample on Get, we'd be able to access legit right padding values. */ + SDL_memset(rpadding, '\0', paddingbytes); + retval = SDL_ResampleAudio(chans, inrate, outrate, lpadding, rpadding, inbuf, inbuflen, outbuf, outbuflen); - return SDL_ResampleAudio(chans, stream->src_rate, stream->dst_rate, state->resampler_state.f, inbuf, inbuflen, outbuf, outbuflen); + /* update our left padding with end of current input, for next run. */ + SDL_memcpy(lpadding, ((const Uint8 *) inbuf) + (inbuflen - paddingbytes), paddingbytes); + + return retval; } static void SDL_ResetAudioStreamResampler(SDL_AudioStream *stream) { - SDL_AudioStreamResamplerState *state = (SDL_AudioStreamResamplerState*)stream->resampler_state; - state->resampler_seeded = SDL_FALSE; + /* set all the left padding to silence. */ + const int inrate = stream->src_rate; + const int outrate = stream->dst_rate; + const int chans = (int) stream->pre_resample_channels; + const int len = ResamplerPadding(inrate, outrate) * chans; + SDL_memset(stream->resampler_state, '\0', len * sizeof (float)); } static void @@ -1302,7 +1310,9 @@ SDL_NewAudioStream(const SDL_AudioFormat src_format, #endif if (!retval->resampler_func) { - retval->resampler_state = SDL_calloc(1, sizeof(SDL_AudioStreamResamplerState)); + const int chans = (int) pre_resample_channels; + const int len = ResamplerPadding(src_rate, dst_rate) * chans; + retval->resampler_state = SDL_calloc(len, sizeof (float)); if (!retval->resampler_state) { SDL_FreeAudioStream(retval); SDL_OutOfMemory();