Sync Issue - Audio delay 1.1 seconds

[sbkomurcu]

Hi, first of all, thanks for the Picam project! I have never been able to get the audio to sync up ( apart from static delay) with the video. Thanks to the Picam, this just works amazing!

However, the audio record starts ~1.1 seconds later than the video. Therefore video and audio are not synced unless I modify the output by shifting audio 1.1 seconds at the outputting.

Thus, I would like to ask you if it is possible to add ~1.1 seconds delay for the video record to initiate? Or what other solution would you suggest?

Regards,

[iizukanao]

Hi, thanks for using picam!
You might want to check your ALSA configuration. What's your ALSA configuration for the USB microphone? You should use a device name that starts with hw: like hw:1,0.

[sbkomurcu]

Hello! I am using i2s mems mic (sph0645) with the following configuration; ./picam -w 1920 -h 1080 -f 30 --alsadev plug:dmic_hw --volume 5. When I use hw:1,0 capturing started without error but there is also no sound at the output. Therefore I used the command --alsadev plug:dmic_hw in which sound is recorded perfectly but must be shifted 1.1 seconds.

[iizukanao]

Hmm, I'm not sure why it introduces 1.1 seconds of delay. Have you tried plughw:<num>? You can find the <num> by running arecord -l.

[sbkomurcu]

Thanks for the suggestion! Unfortunately, I was not able to fix the issue based on your suggestion. Use of plughw:<num> (i.e. plughw:0,0) lead me to an issue which is discussed in #86. On the other hand, the use of plug:dmic_sv leads me to the same issue mentioned in #115.

Therefore I am only able to get a proper audio record by using plug:dmic_hw, but with a sync issue.
Since the amount of delay is static throughout the whole record, I was able to fix the issue by doing a workaround during the conversion from .ts to .mp4 by following the command below;

ffmpeg -i [FILE_NAME].ts -itsoffset -0.4 -i [FILE_NAME].ts -map 0:0 -map 1:1 -acodec copy -vcodec copy synced.mp4
where -itsoffset <NUM> is used to adjust the shifting of the audio track during the conversion process.

Regards!

[brainrecall]

Hmm, I have the same issue, but I'm streaming and not recording. I had to setup a virtual alsa device to merge channels to workaround the slow audio (merge two channels into one). Are there other alsa settings that you know of that could be tweaked?

[feacluster]

I have the issue with the Samson Go mic. I tried doing all the suggestion, but eventually what worked was using ffmpeg to fix it during the TS to MP4 conversion:

ffmpeg -i $file -itsoffset -1.1 -i $file -map 0:0 -map 1:1 -c:v copy -c:a copy -bsf:a aac_adtstoasc test.mp4 > /dev/null 2>&1

For me 1.1 seconds seems to produce perfectly synced audio/video.