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moOde sources and configs
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Bluetooth audio latency increases over time #112

Closed TeChn4K closed 4 years ago

TeChn4K commented 4 years ago

Hi Moode team,

I often use Moode with the Bluetooth renderer, paired with my laptop, audio output to local and buffer set to 20ms.

I notice that almost every time, Bluetooth audio latency increases from unnoticeable to maybe 300 / 500ms. Some times it happens at the very beginning of my session (less than one minute playback), but each time after a longer period (45min / 1h). I have to disconnect & reconnect Bluetooth to reset the latency.

Issue happens from at least Moode 6.4 to 6.5.2 Do you have any idea about how to track down this issue?

Configuration :

moodeaudio commented 4 years ago

What is the format of the audio file? How are you able to measure the latency?

TeChn4K commented 4 years ago

I use bluetooth to send audio from my computer (Youtube or VLC). I did not measure the latency precisely. I'm able to see it when I watch video and notice the lip sync delay.

Audio information details : 

Input / Output
Source: Bluetooth stream
Encoded at: Unknown
Decoded to: 16 bit, 44.1 kHz, Stereo, VBR
Destination: Local
Output rate: 32 bit, 44.1 kHz, Stereo, 2.822 Mbps

DSP operations 
Volume ctl: Software (MPD 32-bit float with dither)
Resampling: n/a
Polarity inv: n/a
Crossfade: n/a
Crossfeed: n/a
Parametric EQ: n/a
Graphic EQ: n/a
Replaygain: n/a
Normalize vol: n/a
Chip options: None

Audio Device
Device: USB audio device
Chip: 
Interface: USB
Formats: S32_LE
Platform: Allo USBridge SIG [CM3+ Lite 1GB v1.0]
moodeaudio commented 4 years ago

The only option in moOde that could affect BT latency is the buffer length setting in BlueZ config.

The lib-sync issue with YT video has been around for ages but I don't recall any issues when using Airplay. Maybe give that a try.

TeChn4K commented 4 years ago

I've tried with buffer length set to 20, 40 and 60ms. For me, these latencies are almost unnoticeable when you watch a video of somebody speaking.

Just to be clear: most of the time, bluetooth latency is perfectly OK and in perfect adequacy with the BlueZ config. You can watch a YT video with no issue at all.

What I'm talking about is a shift issue of the latency. One moment everything is fine, latency is OK, then randomly the latency shift instantly to something unbearable. I'm forced to switch on/off bluetooth connection to reset it.

moodeaudio commented 4 years ago

I don't know what could be causing the latency to suddenly shift or how to troubleshoot something like this. The buffer length setting is a bluez-alsa option so maybe posting the issue to bluez-alsa repo could shed some light on what's happening.

pi@rp3:~ $ cat /etc/bluealsaaplay.conf
# bluealsaaplay.conf
AUDIODEV=plughw:0,0
BUFFERTIME=500000