diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch | 90 |
1 files changed, 0 insertions, 90 deletions
diff --git a/target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch b/target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch deleted file mode 100644 index 8bf1ad80ce..0000000000 --- a/target/linux/brcm2708/patches-4.4/0133-bcm2835-interpolate-audio-delay.patch +++ /dev/null @@ -1,90 +0,0 @@ -From a94c77d797c554678a37fb2b921fbab46f7f205e 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. ---- - sound/arm/bcm2835-pcm.c | 12 +++++++++++- - sound/arm/bcm2835.h | 1 + - 2 files changed, 12 insertions(+), 1 deletion(-) - ---- a/sound/arm/bcm2835-pcm.c -+++ b/sound/arm/bcm2835-pcm.c -@@ -25,7 +25,7 @@ - /* hardware definition */ - static 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, -@@ -99,6 +99,8 @@ static irqreturn_t bcm2835_playback_fifo - 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); -@@ -399,6 +401,7 @@ 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, -@@ -495,6 +498,7 @@ snd_bcm2835_pcm_pointer(struct snd_pcm_s - { - struct snd_pcm_runtime *runtime = substream->runtime; - bcm2835_alsa_stream_t *alsa_stream = runtime->private_data; -+ u64 now = ktime_get_ns(); - - audio_info(" .. IN\n"); - -@@ -503,6 +507,12 @@ snd_bcm2835_pcm_pointer(struct snd_pcm_s - 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); -+ - audio_info(" .. OUT\n"); - return snd_pcm_indirect_playback_pointer(substream, - &alsa_stream->pcm_indirect, ---- a/sound/arm/bcm2835.h -+++ b/sound/arm/bcm2835.h -@@ -137,6 +137,7 @@ typedef struct bcm2835_alsa_stream { - unsigned int pos; - unsigned int buffer_size; - unsigned int period_size; -+ u64 interpolate_start; - - uint32_t enable_fifo_irq; - irq_handler_t fifo_irq_handler; |