diff options
| -rw-r--r-- | libavdevice/alsa-audio-dec.c | 5 | ||||
| -rw-r--r-- | libavdevice/jack_audio.c | 5 | ||||
| -rw-r--r-- | libavdevice/timefilter.c | 19 | ||||
| -rw-r--r-- | libavdevice/timefilter.h | 10 |
4 files changed, 22 insertions, 17 deletions
diff --git a/libavdevice/alsa-audio-dec.c b/libavdevice/alsa-audio-dec.c index f2dd21655b..62bf42d272 100644 --- a/libavdevice/alsa-audio-dec.c +++ b/libavdevice/alsa-audio-dec.c @@ -59,7 +59,6 @@ static av_cold int audio_read_header(AVFormatContext *s1) AVStream *st; int ret; enum CodecID codec_id; - double o; st = avformat_new_stream(s1, NULL); if (!st) { @@ -81,9 +80,9 @@ static av_cold int audio_read_header(AVFormatContext *s1) st->codec->sample_rate = s->sample_rate; st->codec->channels = s->channels; avpriv_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */ - o = 2 * M_PI * s->period_size / s->sample_rate * 1.5; // bandwidth: 1.5Hz + /* microseconds instead of seconds, MHz instead of Hz */ s->timefilter = ff_timefilter_new(1000000.0 / s->sample_rate, - sqrt(2 * o), o * o); + s->period_size, 1.5E-6); if (!s->timefilter) goto fail; diff --git a/libavdevice/jack_audio.c b/libavdevice/jack_audio.c index 257a291758..1fa4f86724 100644 --- a/libavdevice/jack_audio.c +++ b/libavdevice/jack_audio.c @@ -145,7 +145,6 @@ static int start_jack(AVFormatContext *context) JackData *self = context->priv_data; jack_status_t status; int i, test; - double o, period; /* Register as a JACK client, using the context filename as client name. */ self->client = jack_client_open(context->filename, JackNullOption, &status); @@ -181,9 +180,7 @@ static int start_jack(AVFormatContext *context) jack_set_xrun_callback(self->client, xrun_callback, self); /* Create time filter */ - period = (double) self->buffer_size / self->sample_rate; - o = 2 * M_PI * 1.5 * period; /// bandwidth: 1.5Hz - self->timefilter = ff_timefilter_new (1.0 / self->sample_rate, sqrt(2 * o), o * o); + self->timefilter = ff_timefilter_new (1.0 / self->sample_rate, self->buffer_size, 1.5); /* Create FIFO buffers */ self->filled_pkts = av_fifo_alloc(FIFO_PACKETS_NUM * sizeof(AVPacket)); diff --git a/libavdevice/timefilter.c b/libavdevice/timefilter.c index e225ed11a9..4b8a10cb40 100644 --- a/libavdevice/timefilter.c +++ b/libavdevice/timefilter.c @@ -36,14 +36,21 @@ struct TimeFilter { int count; }; -TimeFilter *ff_timefilter_new(double clock_period, - double feedback2_factor, - double feedback3_factor) +/* 1 - exp(-x) using a 3-order power series */ +static double qexpneg(double x) +{ + return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3))); +} + +TimeFilter *ff_timefilter_new(double time_base, + double period, + double bandwidth) { TimeFilter *self = av_mallocz(sizeof(TimeFilter)); - self->clock_period = clock_period; - self->feedback2_factor = feedback2_factor; - self->feedback3_factor = feedback3_factor; + double o = 2 * M_PI * bandwidth * period * time_base; + self->clock_period = time_base; + self->feedback2_factor = qexpneg(M_SQRT2 * o); + self->feedback3_factor = qexpneg(o * o); return self; } diff --git a/libavdevice/timefilter.h b/libavdevice/timefilter.h index 2a77946e99..33862f63bb 100644 --- a/libavdevice/timefilter.h +++ b/libavdevice/timefilter.h @@ -45,16 +45,18 @@ typedef struct TimeFilter TimeFilter; * * Unless you know what you are doing, you should set these as follow: * - * o = 2 * M_PI * bandwidth * period - * feedback2_factor = sqrt(2 * o) + * o = 2 * M_PI * bandwidth * period_in_seconds + * feedback2_factor = sqrt(2) * o * feedback3_factor = o * o * * Where bandwidth is up to you to choose. Smaller values will filter out more * of the jitter, but also take a longer time for the loop to settle. A good * starting point is something between 0.3 and 3 Hz. * - * @param clock_period period of the hardware clock in seconds - * (for example 1.0/44100) + * @param time_base period of the hardware clock in seconds + * (for example 1.0/44100) + * @param period expected update interval, in input units + * @param brandwidth filtering bandwidth, in Hz * * For more details about these parameters and background concepts please see: * http://www.kokkinizita.net/papers/usingdll.pdf |