diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.19/950-0135-bcm2835-interpolate-audio-delay.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.19/950-0135-bcm2835-interpolate-audio-delay.patch | 89 |
1 files changed, 0 insertions, 89 deletions
diff --git a/target/linux/brcm2708/patches-4.19/950-0135-bcm2835-interpolate-audio-delay.patch b/target/linux/brcm2708/patches-4.19/950-0135-bcm2835-interpolate-audio-delay.patch deleted file mode 100644 index 55cd26b25b..0000000000 --- a/target/linux/brcm2708/patches-4.19/950-0135-bcm2835-interpolate-audio-delay.patch +++ /dev/null @@ -1,89 +0,0 @@ -From 652b0ec2ab2d2e2af7bb4f7d62a4020a20720677 Mon Sep 17 00:00:00 2001 -From: wm4 <wm4@nowhere> -Date: Wed, 13 Jan 2016 19:44:47 +0100 -Subject: [PATCH] bcm2835: interpolate audio delay - -It appears the GPU only sends us a message all 10ms to update -the playback progress. Other than this, the playback position -(what SNDRV_PCM_IOCTL_DELAY will return) is not updated at all. -Userspace will see jitter up to 10ms in the audio position. - -Make this a bit nicer for userspace by interpolating the -position using the CPU clock. - -I'm not sure if setting snd_pcm_runtime.delay is the right -approach for this. Or if there is maybe an already existing -mechanism for position interpolation in the ALSA core. - -I only set SNDRV_PCM_INFO_BATCH because this appears to remove -at least one situation snd_pcm_runtime.delay is used, so I have -to worry less in which place I have to update this field, or -how it interacts with the rest of ALSA. - -In the future, it might be nice to use VC_AUDIO_MSG_TYPE_LATENCY. -One problem is that it requires sending a videocore message, and -waiting for a reply, which could make the implementation much -harder due to locking and synchronization requirements. ---- - .../vc04_services/bcm2835-audio/bcm2835-pcm.c | 12 +++++++++++- - .../staging/vc04_services/bcm2835-audio/bcm2835.h | 1 + - 2 files changed, 12 insertions(+), 1 deletion(-) - ---- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c -+++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c -@@ -11,7 +11,7 @@ - /* hardware definition */ - static const struct snd_pcm_hardware snd_bcm2835_playback_hw = { - .info = (SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER | -- SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID), -+ SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID | SNDRV_PCM_INFO_BATCH), - .formats = SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S16_LE, - .rates = SNDRV_PCM_RATE_CONTINUOUS | SNDRV_PCM_RATE_8000_48000, - .rate_min = 8000, -@@ -81,6 +81,8 @@ void bcm2835_playback_fifo(struct bcm283 - alsa_stream->pos %= alsa_stream->buffer_size; - } - -+ alsa_stream->interpolate_start = ktime_get_ns(); -+ - if (alsa_stream->substream) { - if (new_period) - snd_pcm_period_elapsed(alsa_stream->substream); -@@ -306,6 +308,7 @@ static int snd_bcm2835_pcm_prepare(struc - alsa_stream->buffer_size = snd_pcm_lib_buffer_bytes(substream); - alsa_stream->period_size = snd_pcm_lib_period_bytes(substream); - alsa_stream->pos = 0; -+ alsa_stream->interpolate_start = ktime_get_ns(); - - audio_debug("buffer_size=%d, period_size=%d pos=%d frame_bits=%d\n", - alsa_stream->buffer_size, alsa_stream->period_size, -@@ -397,12 +400,19 @@ snd_bcm2835_pcm_pointer(struct snd_pcm_s - { - struct snd_pcm_runtime *runtime = substream->runtime; - struct bcm2835_alsa_stream *alsa_stream = runtime->private_data; -+ u64 now = ktime_get_ns(); - - audio_debug("pcm_pointer... (%d) hwptr=%d appl=%d pos=%d\n", 0, - frames_to_bytes(runtime, runtime->status->hw_ptr), - frames_to_bytes(runtime, runtime->control->appl_ptr), - alsa_stream->pos); - -+ /* Give userspace better delay reporting by interpolating between GPU -+ * notifications, assuming audio speed is close enough to the clock -+ * used for ktime */ -+ if (alsa_stream->interpolate_start && alsa_stream->interpolate_start < now) -+ runtime->delay = -(int)div_u64((now - alsa_stream->interpolate_start) * runtime->rate, 1000000000); -+ - return snd_pcm_indirect_playback_pointer(substream, - &alsa_stream->pcm_indirect, - alsa_stream->pos); ---- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h -+++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h -@@ -133,6 +133,7 @@ struct bcm2835_alsa_stream { - unsigned int pos; - unsigned int buffer_size; - unsigned int period_size; -+ u64 interpolate_start; - - atomic_t retrieved; - struct bcm2835_audio_instance *instance; |