tinyloop

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tinyloop

• tinyloop is a raspberry pi image for video installations.
• No need to log in; drag-and-drop video files onto the SD card itself, or onto an attached USB drive. Headless setup, plug-and-play.
• Playback mode determined by the media content loaded:
  • Perfect seamless gapless endless looping of video with sound
  • Perfect seamless gapless endless looping of video
  • Looping playlist of multiple video files, with sound (gaps between files)
  • Loop a single file (as gapless as omxplayer can manage)
  • Simple scripting, e.g. a short seamless video loop with a long gapless mix of audio files
• Comes with sample content showing all playback modes.
• Read-only system for reliability; no shutdown needed, simply unplug.
• Tested on rpi zero, zero w, and the original 1a.
• Modern filesystem (NTFS, HFS+, ETX4) and large file support.
• tiny; < 2GB, leaving plenty of space for media files. Power to video in 17 seconds.

Setup

1. Flash the image (e.g. with Pi Filler) onto an 8GB or larger SD Card.
2. Drag-and-drop video content into the DATA partition. Feel free to resize or reformat the DATA partition (FAT32, NTFS, HFS+, EXT4). Windows will not display all partitions on an SD card which makes drag-and-drop difficult; the simplest solution is to put the media on a USB thumb drive instead.
3. Plug and play. Connect the HDMI and turn on display before powering on the rpi.

Media Formatting

For seamless audio-video looping:

Edit your content into a single file (max 1080p 30fps) and use ffmpeg to extract the audio and video into two files:

ffmpeg -i Desktop/perkitchen.MP4 -f s16le -acodec pcm_s16le -ar 48000 -ac 2 perkitchen.raw

ffmpeg -i Desktop/perkitchen.MP4 -an -f h264 -pix_fmt yuv420p perkitchen.h264

NOTE: for many media files, the audio and video playback times do not exactly match. If the loops start to drift, tinyloop will perform an audio micro-edit to nudge them back into sync. For most content this is imperceptible. In my experience a typical file will loop several times before requiring a microedit. If you carefully calculate the audio file's length to exactly match the number of frames, it might get nudged only once every 100 or 1000 loops, or never.

For seamless video looping:

Edit your content into a single file (max 1080p 30fps) and use ffmpeg to extract the video:

ffmpeg -i Desktop/perkitchen.MP4 -an -f h264 -pix_fmt yuv420p perkitchen.h264

For a playlist:

Put your files into a folder named "playlist". Supports any format omxplayer does (most of them.)

For a single file:

Drag-and-drop it. The first file found will loop. Supports any format omxplayer does (most of them.)

Scripting:

Load an executable video.sh file in addition to any media files it needs. See the preloaded example. This is also an easy way to customize the builtin scripts, e.g. to send audio to headphone out or enable subtitles.

Q&A

Why?

At time of creation, I had to choose between several images depending on what type of playback I desired, and I couldn't find a working solution for gapless looping with sound.

How can I hack the image?

rename video__login_prompt.sh to video.sh, power up, ctrl-alt-f2, log in with pi/raspberry

sudo mount -o remount,rw /boot

sudo mount -o remount,rw /

For seamless looping, how do I calculate optimum audio file length?

Take the number of video_frames printed by ffmpeg when extracting video. Keep the video at 30FPS [or 24FPS] and make sure the audio is 1470 [or 2000] audio frames per video frame (file size should be 5880 bytes [or 8000 bytes] * video_frames). If your video is 29.97, either re-encode it to 30, or perform the following math:

audio_frames = video_frames * 48000 / 29.97

Throw away anything past the decimal point

Target_file_size = 4 * audio_frames

The result will be within 1 audio frame of target, and will drift so slowly that there should be one micro-edit every thousand or so loops.

That video "extraction" is actually a reencode!

I don't like it either. If you already have yuv420p .h264, it should be possible to demux it, e.g. yamb or various other tools. It should also be possible to invoke ffmpeg with -c:v copy to avoid re-encoding, although it didn't work for me. My workflow is to render to apple prores and leave the encoding for ffmpeg.

How can I improve H264 quality?

The default h264 quality works pretty well, but if you get blocky artifacts or other problems in your output file, explore the filters and options. A good place to start is adding "-crf 17".

How can I get analog output?

If you don't connect an HDMI cable but do connect a composite cable, you should get video on the composite output. This has been tested on an rPi 1a. In extreme cases when you don't get a signal on your composite (or HDMI) display, advanced video options can be set by editing config.txt in the boot/ partition.

Support

No support promised, but provided on best effort basis.

Support accepted; although everything builds on work done by the community, programming the seamless audio-video looping and setting up the image took quite a few hours.

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