From 8b4cb54595baeeb1d9b7d11a842ef7946e43a55a Mon Sep 17 00:00:00 2001 From: Maarten Bosmans Date: Fri, 7 Jan 2011 01:25:55 +0100 Subject: Limit rate adjustments to small, inaudible jumps MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The same logic is applied to the sample rate adjustments in module-rtp-recv, module-loopback and module-combine: - Each time an adjustment is made, the new rate can differ at most 2‰ from the old rate. Such a step is equal to 3.5 cents (a cent is 1/100th of a semitone) and as 5 cents is generally considered the smallest observable difference in pitch, this results in inaudible adjustments. - The sample rate of the stream can only differ from the rate of the corresponding sink by 25%. As these adjustments are meant to account for very small clock drifts, any large deviation from the base rate suggests something is seriously wrong. - If the calculated rate is within 20Hz of the base rate, set it to the base rate. This saves CPU because no resampling is necessary. --- src/modules/rtp/module-rtp-recv.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-) (limited to 'src/modules/rtp/module-rtp-recv.c') diff --git a/src/modules/rtp/module-rtp-recv.c b/src/modules/rtp/module-rtp-recv.c index 7dbb1efa..3bbeb1fc 100644 --- a/src/modules/rtp/module-rtp-recv.c +++ b/src/modules/rtp/module-rtp-recv.c @@ -288,6 +288,9 @@ static int rtpoll_work_cb(pa_rtpoll_item *i) { if (s->last_rate_update + RATE_UPDATE_INTERVAL < pa_timeval_load(&now)) { pa_usec_t wi, ri, render_delay, sink_delay = 0, latency, fix; unsigned fix_samples; + uint32_t base_rate = s->sink_input->sink->sample_spec.rate; + uint32_t current_rate = s->sink_input->sample_spec.rate; + uint32_t new_rate; pa_log_debug("Updating sample rate"); @@ -309,7 +312,7 @@ static int rtpoll_work_cb(pa_rtpoll_item *i) { else latency = wi - ri; - pa_log_debug("Write index deviates by %0.2f ms, expected %0.2f ms", (double) latency/PA_USEC_PER_MSEC, (double) s->intended_latency/PA_USEC_PER_MSEC); + pa_log_debug("Write index deviates by %0.2f ms, expected %0.2f ms", (double) latency/PA_USEC_PER_MSEC, (double) s->intended_latency/PA_USEC_PER_MSEC); /* Calculate deviation */ if (latency < s->intended_latency) @@ -320,19 +323,24 @@ static int rtpoll_work_cb(pa_rtpoll_item *i) { /* How many samples is this per second? */ fix_samples = (unsigned) (fix * (pa_usec_t) s->sink_input->thread_info.sample_spec.rate / (pa_usec_t) RATE_UPDATE_INTERVAL); - /* Check if deviation is in bounds */ - if (fix_samples > s->sink_input->sample_spec.rate*.50) - pa_log_debug("Hmmm, rate fix is too large (%lu Hz), not applying.", (unsigned long) fix_samples); - else { - /* Fix up rate */ - if (latency < s->intended_latency) - s->sink_input->sample_spec.rate -= fix_samples; - else - s->sink_input->sample_spec.rate += fix_samples; - - if (s->sink_input->sample_spec.rate > PA_RATE_MAX) - s->sink_input->sample_spec.rate = PA_RATE_MAX; + if (latency < s->intended_latency) + new_rate = current_rate - fix_samples; + else + new_rate = current_rate + fix_samples; + + if (new_rate < (uint32_t) (base_rate*0.8) || new_rate > (uint32_t) (base_rate*1.25)) { + pa_log_warn("Sample rates too different, not adjusting (%u vs. %u).", base_rate, new_rate); + new_rate = base_rate; + } else { + if (base_rate < new_rate + 20 && new_rate < base_rate + 20) + new_rate = base_rate; + /* Do the adjustment in small steps; 2‰ can be considered inaudible */ + if (new_rate < (uint32_t) (current_rate*0.998) || new_rate > (uint32_t) (current_rate*1.002)) { + pa_log_info("New rate of %u Hz not within 2‰ of %u Hz, forcing smaller adjustment", new_rate, current_rate); + new_rate = PA_CLAMP(new_rate, (uint32_t) (current_rate*0.998), (uint32_t) (current_rate*1.002)); + } } + s->sink_input->sample_spec.rate = new_rate; pa_assert(pa_sample_spec_valid(&s->sink_input->sample_spec)); -- cgit