I can post a clip of the audio if you like? There's a continuous buzz (sawtooth like) from the audio. V:PortSettingsChanged: interlace:-1 deinterlace:0 anaglyph:0 par:1.00 display:0 layer:0 alpha:255 aspectMode:0 V:PortSettingsChanged: interlace:0 deinterlace:0 anaglyph:0 par:1.00 display:0 layer:0 alpha:255 aspectMode:0 Subtitle count: 0, state: off, index: 1, delay: 0 Video codec omx-vp8 width 480 height 360 profile -99 fps 30.000000Īudio codec vorbis channels 1 samplerate 44100 bitspersample 16 & the $ omxplayer -display 0 -o local "/home/pi/Videos/Brightgreen displaylink.mp4" Omxplayer - Commandline multimedia player for the Raspberry Pi I've now inserted a Stretch µSD $ uname -a Stage 4 - 2nd-order quantisation noise shaping from 16-bit PCM at 781250Hz to 7-bit PWM samples.Īs I mentioned in my intial email, it's (up to date)jessie. Stage 3 - A final x2 oversampling stage with a length=4 FIR filter, which is folded into the noise shaping for various beneficial reasons. Stage 2 - Oversampling by factor x8 to 390625Hz using a length=512 FIR filter with a nice, sharp cut-off. Stage 1 is source samplerate conversion (8kHz-48kHz -> 48828Hz) - this fractional conversion is required as the PWM source clock is not a power-of-two product of audio sample frequencies. : The signal processing chain implements three resampling stages and a noise shaping stage. Pi 1 A+/B+, Pi 2 and Pi 3 all implement a low-noise "clean" power supply for the analogue audio jack. Original models of Pi (with 26-pin GPIO headers) will suffer from worse background noise performance as there is no dedicated output buffer for the analogue audio jack. : The achievable sound quality depends on the model of Pi used as well as the quality of upstream power supply and lack of ground loops in all connections. This has proven tricky to replicate, so please detail your configuration if you manage to make this bug appear. A workaround is to restart the process in question, as it recovers after force-quitting the hung process.
#Wire hang redux driver
There is currently a known bug where multiple opens/closes of the driver via ALSA can cause the next open to hang. Please test and report back with any issues. As of the time of writing there's no obvious need for a nerfed version of the driver. Once any known incompatibilities are mapped out then they will either be documented or a slightly nerfed driver configuration could be implemented that expends a a few dB of audio quality in exchange for GPU performance. MPEG2 1080i source with DTS or AC3 audio or simultaneous CSI camera encoding + HD content playback). There may be some "busy" use-cases that cause lag such as playback of HD interlaced content with VPU audio decode (e.g. The intention is to move to using this driver as the default analogue output driver for all models of Pi that have the 3.5mm jack. Finer-grained resource locking in the driver means fewer contention points when the VPU is busy on-the-fly switching of audio source between HDMI and Analogue with the driver in use no longer corrupts the analogue output
GPU vector unit utilisation has been reduced significantly as a much more efficient three-stage resampling pipeline is now used The driver now allows for up to 8 simultaneous writers
ALSA and omxplayer running simultaneously) and improvements in the additional GPU load the driver causes. The driver has undergone a few modifications that allow for multiple concurrent users (i.e. This is a continuation of the last thread which I closed as it contains a lot of previous bughunting activity that's no longer relevant. It works by oversampling the audio stream by a high factor and then pushing the quantisation noise away from audible frequencies by a technique known as sigma-delta noise shaping.
The analogue signal-to-noise ratio now approaches CD quality with this driver. Available in latest Raspbian is a PWM audio driver that significantly increases the audio quality available from the 3.5mm TRRS jack.
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