| Message ID | 20180105221242.22083-1-mka@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
El Fri, Jan 05, 2018 at 02:12:42PM -0800 Matthias Kaehlcke ha dit: > The Rockchip I2S controller only allows to configure even numbers of > capture channels. It is still possible to capture monophonic audio by > using dual-channel mode and ignoring the 'data' from the second > channel. Due to different issues in our audio recording path I couldn't test this properly, and only looked at the .wav data in audacity, which appeared to look ok. After putting some of the missing pieces together and I noticed that mono capture doesn't work as intended, the recorded audio is slowed down. I think this is because the I2S controller keeps generating a two-channel stream, however the sound system interprets it as a monophonic stream because of the channel configuration. Not sure if there is a clean solution for this if we can't tell the hardware to generate a single-channel stream. Any suggestions or do we have to revert the patch? Sorry about the mess :( > --- > sound/soc/rockchip/rockchip_i2s.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c > index 908211e1d6fc..cc22ab3d10dd 100644 > --- a/sound/soc/rockchip/rockchip_i2s.c > +++ b/sound/soc/rockchip/rockchip_i2s.c > @@ -328,6 +328,7 @@ static int rockchip_i2s_hw_params(struct snd_pcm_substream *substream, > val |= I2S_CHN_4; > break; > case 2: > + case 1: > val |= I2S_CHN_2; > break; > default: > @@ -460,7 +461,7 @@ static struct snd_soc_dai_driver rockchip_i2s_dai = { > }, > .capture = { > .stream_name = "Capture", > - .channels_min = 2, > + .channels_min = 1, > .channels_max = 2, > .rates = SNDRV_PCM_RATE_8000_192000, > .formats = (SNDRV_PCM_FMTBIT_S8 | > @@ -654,7 +655,7 @@ static int rockchip_i2s_probe(struct platform_device *pdev) > } > > if (!of_property_read_u32(node, "rockchip,capture-channels", &val)) { > - if (val >= 2 && val <= 8) > + if (val >= 1 && val <= 8) > soc_dai->capture.channels_max = val; > } >
On Mon, Jan 08, 2018 at 04:01:15PM -0800, Matthias Kaehlcke wrote: > Due to different issues in our audio recording path I couldn't test > this properly, and only looked at the .wav data in audacity, which > appeared to look ok. After putting some of the missing pieces > together and I noticed that mono capture doesn't work as intended, > the recorded audio is slowed down. I think this is because the I2S > controller keeps generating a two-channel stream, however the sound > system interprets it as a monophonic stream because of the channel > configuration. That seems odd - I'd expect underruns somewhere? > Not sure if there is a clean solution for this if we can't tell the > hardware to generate a single-channel stream. Any suggestions or do > we have to revert the patch? It sounds like a very standard problem with I2S devices, it's a fundamentally stereo format after all. If you can't get it to discard the second channel there's probably not much doing.
diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c index 908211e1d6fc..cc22ab3d10dd 100644 --- a/sound/soc/rockchip/rockchip_i2s.c +++ b/sound/soc/rockchip/rockchip_i2s.c @@ -328,6 +328,7 @@ static int rockchip_i2s_hw_params(struct snd_pcm_substream *substream, val |= I2S_CHN_4; break; case 2: + case 1: val |= I2S_CHN_2; break; default: @@ -460,7 +461,7 @@ static struct snd_soc_dai_driver rockchip_i2s_dai = { }, .capture = { .stream_name = "Capture", - .channels_min = 2, + .channels_min = 1, .channels_max = 2, .rates = SNDRV_PCM_RATE_8000_192000, .formats = (SNDRV_PCM_FMTBIT_S8 | @@ -654,7 +655,7 @@ static int rockchip_i2s_probe(struct platform_device *pdev) } if (!of_property_read_u32(node, "rockchip,capture-channels", &val)) { - if (val >= 2 && val <= 8) + if (val >= 1 && val <= 8) soc_dai->capture.channels_max = val; }
The Rockchip I2S controller only allows to configure even numbers of capture channels. It is still possible to capture monophonic audio by using dual-channel mode and ignoring the 'data' from the second channel. Signed-off-by: Matthias Kaehlcke <mka@chromium.org> --- sound/soc/rockchip/rockchip_i2s.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)