From a79eee8d3d8a80c37d235e1181d67c3705c7bbfe Mon Sep 17 00:00:00 2001 From: Luke Ross Date: Tue, 29 Aug 2006 10:46:32 +0200 Subject: [ALSA] Support for non-standard rates in USB audio driver There's at least one USB audio chipset out there which supports only one non-standard rate (ID 0e6a:0310 supports 46875Hz). There's a few other patches for this card which are unsatisfactory because they attempt to map this rate to 44.1k leading to sound distortion. The patch below uses SNDRV_PCM_RATE_KNOT to properly support the non-standard rates where they are available. Signed-off-by: Luke Ross Signed-off-by: Takashi Iwai Signed-off-by: Jaroslav Kysela --- sound/usb/usbaudio.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) (limited to 'sound/usb/usbaudio.c') diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c index 087f9b64d8a..664dd4c21e6 100644 --- a/sound/usb/usbaudio.c +++ b/sound/usb/usbaudio.c @@ -123,6 +123,7 @@ struct audioformat { unsigned int rate_min, rate_max; /* min/max rates */ unsigned int nr_rates; /* number of rate table entries */ unsigned int *rate_table; /* rate table */ + unsigned int needs_knot; /* any unusual rates? */ }; struct snd_usb_substream; @@ -1759,6 +1760,9 @@ static int check_hw_params_convention(struct snd_usb_substream *subs) } channels[f->format] |= (1 << f->channels); rates[f->format] |= f->rates; + /* needs knot? */ + if (f->needs_knot) + goto __out; } /* check whether channels and rates match for all formats */ cmaster = rmaster = 0; @@ -1799,6 +1803,38 @@ static int check_hw_params_convention(struct snd_usb_substream *subs) return err; } +/* + * If the device supports unusual bit rates, does the request meet these? + */ +static int snd_usb_pcm_check_knot(struct snd_pcm_runtime *runtime, + struct snd_usb_substream *subs) +{ + struct list_head *p; + struct snd_pcm_hw_constraint_list constraints_rates; + int err; + + list_for_each(p, &subs->fmt_list) { + struct audioformat *fp; + fp = list_entry(p, struct audioformat, list); + + if (!fp->needs_knot) + continue; + + constraints_rates.count = fp->nr_rates; + constraints_rates.list = fp->rate_table; + constraints_rates.mask = 0; + + err = snd_pcm_hw_constraint_list(runtime, 0, + SNDRV_PCM_HW_PARAM_RATE, + &constraints_rates); + + if (err < 0) + return err; + } + + return 0; +} + /* * set up the runtime hardware information. @@ -1861,6 +1897,8 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre SNDRV_PCM_HW_PARAM_CHANNELS, -1)) < 0) return err; + if ((err = snd_usb_pcm_check_knot(runtime, subs)) < 0) + return err; } return 0; } @@ -2406,6 +2444,7 @@ static int parse_audio_format_rates(struct snd_usb_audio *chip, struct audioform unsigned char *fmt, int offset) { int nr_rates = fmt[offset]; + int found; if (fmt[0] < offset + 1 + 3 * (nr_rates ? nr_rates : 2)) { snd_printk(KERN_ERR "%d:%u:%d : invalid FORMAT_TYPE desc\n", chip->dev->devnum, fp->iface, fp->altsetting); @@ -2428,6 +2467,7 @@ static int parse_audio_format_rates(struct snd_usb_audio *chip, struct audioform return -1; } + fp->needs_knot = 0; fp->nr_rates = nr_rates; fp->rate_min = fp->rate_max = combine_triple(&fmt[8]); for (r = 0, idx = offset + 1; r < nr_rates; r++, idx += 3) { @@ -2436,13 +2476,19 @@ static int parse_audio_format_rates(struct snd_usb_audio *chip, struct audioform fp->rate_min = rate; else if (rate > fp->rate_max) fp->rate_max = rate; + found = 0; for (c = 0; c < (int)ARRAY_SIZE(conv_rates); c++) { if (rate == conv_rates[c]) { + found = 1; fp->rates |= (1 << c); break; } } + if (!found) + fp->needs_knot = 1; } + if (fp->needs_knot) + fp->rates |= SNDRV_PCM_RATE_KNOT; } else { /* continuous rates */ fp->rates = SNDRV_PCM_RATE_CONTINUOUS; -- cgit v1.2.3