Mp4 file stutters when 3 images + 1 text label are displayed about info-beamer-nodes

[dividuum]

Interesting. I never had audio slow down. But displaying a lot at once certainly puts a lot of load on the GPU. What the frame rate while displaying all your content? Is it still at 60? Using images identical to the target resolution certainly helps at bit, so I suggest you try that first. You can also use INFOBEAMER_SWAP_INTERVAL=2 to see how everything works if you go down to 30fps. Power might be an issue, but that would usually result in a visual indicator on screen.

[zontarian]

Hi. Interesting is not what I said :)

Ok.. I was aware of the visual indicator (the Harry Potter flash icon).. but there is no such.
I've tried with INFOBEAMER_SWAP_INTERVAL=2 but to me it seems the same. It stutters after a few seconds..

Btw, is there an audio only file format ? I've tried with WAV but it's not played, so I've used iMovie (!!) to create a video with a fake image and the audio track.. and exported it to mp4.

Now I'll try resizing.
Thanks

[zontarian]

Ok.. after reducing image from 1900x2048 to almost half each size.. it works a little longer before stuttering. 8 seconds instead of 4..

As a side note, I've tried to reduce the number of images loaded at any given time.
Now I have only a background image, a priority image and the mp4. Everything else is swapped out, discarded, a part ffrom the loop video which is paused.

Again, this results in a longer time of normal audio (20 sec?) and the stutter takes longer to appear, but it appears anyway.. :(

Weird thing is.. If I play a proper video +audio instead of fake video+audio, of about the same size on disk, but without the priority image, the video is supersmooth..

[dividuum]

Could you send me the node directory, so I can try to run it on one of my Pis?

[zontarian]

Mh.. not really. It's my customer copyrighted material but, most important, it's 1.5 GB in around 340 files.
I've solved by treating this edge case with a trick: instead of composing two images (1020x800) I show an already composed image (just one) and the audio plays smoothly..

If you think I could share only the relevant files privately?

[dividuum]

Understood. The workaround is a good idea in general. The Pi isn't too powerful and the more you can "cheat" the better. Sure about sharing the files privately (and offering any result publicly).

[zontarian]

In the end with the good help of @dividuum , we ended using a simple MP4 file with a transparent still image. This way the decoding is lighter and it works.

This is the script we used to pass from wav to mp4

ffmpeg -y -i original.wav audio_only.aac # get audio part
ffmpeg -y -loop 1  -i blank.png -i audio_only.aac -c:v libx264 -r 5 -b:v 10000 -pix_fmt yuv420p -c:a copy -shortest only_audio.mp4

blang.png is a simple 16x16 transparent PNG

Thanks!