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Subject: alsa: Fix not being able to get a larger latency on capture devices with small max period sizes Author: Hans de Goede <[email protected]> Date: Mon Feb 1 21:43:37 2016 +0100 On some capture devices (e.g. bttv cards) the max period size is somewhat small. Since we only use 2 perios on these devices we end up with only allowing small latencies, which is a problem when e.g. using a usb codec as output. This commit fixes this by adjusting the amount of periods on the capture side when this happens. Signed-off-by: Hans de Goede <[email protected]> common/alsa_stream.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) --- http://git.linuxtv.org/cgit.cgi/xawtv3.git/commit/?id=daf4665a0d3c1af65b31887575ea8848ad71ace2 diff --git a/common/alsa_stream.c b/common/alsa_stream.c index 3e33b5e5f7ba..1165554f8e23 100644 --- a/common/alsa_stream.c +++ b/common/alsa_stream.c @@ -109,9 +109,10 @@ static void getparams_periods(snd_pcm_t *handle, snd_pcm_hw_params_t *params, unsigned int *usecs, unsigned int *count, - const char *id) + int allow_adjust, const char *id) { unsigned min = 0, max = 0; + unsigned desired = *usecs * *count; snd_pcm_hw_params_get_periods_min(params, &min, 0); snd_pcm_hw_params_get_periods_max(params, &max, 0); @@ -137,6 +138,13 @@ static void getparams_periods(snd_pcm_t *handle, if (*usecs > max) *usecs = max; } + + /* If we deviate from the desired size by more then 20% adjust count */ + if (allow_adjust && (((*usecs * *count) < (desired * 8 / 10)) || + ((*usecs * *count) > (desired * 12 / 10)))) { + *count = (desired + *usecs / 2) / *usecs; + getparams_periods(handle, params, usecs, count, 0, id); + } } static int setparams_periods(snd_pcm_t *handle, @@ -351,12 +359,16 @@ static int setparams(snd_pcm_t *phandle, snd_pcm_t *chandle, /* Negotiate period parameters */ c_periodtime = latency * 1000 / c_periods; - getparams_periods(chandle, c_hwparams, &c_periodtime, &c_periods, "capture"); + getparams_periods(chandle, c_hwparams, &c_periodtime, &c_periods, 1, "capture"); p_periods = c_periods * 2; p_periodtime = c_periodtime; - getparams_periods(phandle, p_hwparams, &p_periodtime, &p_periods, "playback"); + getparams_periods(phandle, p_hwparams, &p_periodtime, &p_periods, 0, "playback"); c_periods = p_periods / 2; + if (verbose) + fprintf(error_fp, "alsa: Capture %u periods of %u usecs, Playback %u periods of %u usecs\n", + c_periods, c_periodtime, p_periods, p_periodtime); + /* * Some playback devices support a very limited periodtime range. If the user needs to * use a higher latency to avoid overrun/underrun, use an alternate algorithm of incresing @@ -365,10 +377,10 @@ static int setparams(snd_pcm_t *phandle, snd_pcm_t *chandle, if (p_periodtime < c_periodtime) { c_periodtime = p_periodtime; c_periods = round (latency * 1000.0 / c_periodtime + 0.5); - getparams_periods(chandle, c_hwparams, &c_periodtime, &c_periods, "capture"); + getparams_periods(chandle, c_hwparams, &c_periodtime, &c_periods, 0, "capture"); p_periods = c_periods * 2; p_periodtime = c_periodtime; - getparams_periods(phandle, p_hwparams, &p_periodtime, &p_periods, "playback"); + getparams_periods(phandle, p_hwparams, &p_periodtime, &p_periods, 0, "playback"); c_periods = p_periods / 2; } _______________________________________________ linuxtv-commits mailing list [email protected] http://www.linuxtv.org/cgi-bin/mailman/listinfo/linuxtv-commits
