empty gif after ffmpeg error "Number of frames to loop is not set"

[raphamorim]

Original issue was made by @TLINDEN in charmbracelet/freeze#168 and it was moved to VHS.

Describe the bug
I have made a rather long tape file which worked fine up to a certain point. But I am unable to find the section of the file which causes the issue. If I comment out all sections, only let one section uncommented and then execute vhs, then it works every time. However, if all sections are enabled, then it fails. So I think the tape file has no errors.

When the issue happens, an empty gif will be created and ffmeg shows an error message.

To Reproduce
Steps to reproduce the behavior:

1. Clone https://github.com/tlinden/anydb/
2. git checkout feature/vhs-demo
3. go build
4. cd demo
5. make (this actually executes vhs)

Expected behavior
A gif should have been created.

Screenshots

[..]
Sleep 4s

Creating demo.gif...
ffmpeg version 7.0.2-3ubuntu1 Copyright (c) 2000-2024 the FFmpeg developers
  built with gcc 14 (Ubuntu 14.2.0-2ubuntu1)
  configuration: --prefix=/usr --extra-version=3ubuntu1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --disable-libmfx --disable-omx --enable-gnutls --enable-libaom --enable-libass --enable-libbs2b --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libharfbuzz --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-openal --enable-opencl --enable-opengl --disable-sndio --enable-libvpl --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-ladspa --enable-libbluray --enable-libcaca --enable-libdvdnav --enable-libdvdread --enable-libjack --enable-libpulse --enable-librabbitmq --enable-librist --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libx264 --enable-libzmq --enable-libzvbi --enable-lv2 --enable-sdl2 --enable-libplacebo --enable-librav1e --enable-pocketsphinx --enable-librsvg --enable-libjxl --enable-shared
  libavutil      59.  8.100 / 59.  8.100
  libavcodec     61.  3.100 / 61.  3.100
  libavformat    61.  1.100 / 61.  1.100
  libavdevice    61.  1.100 / 61.  1.100
  libavfilter    10.  1.100 / 10.  1.100
  libswscale      8.  1.100 /  8.  1.100
  libswresample   5.  1.100 /  5.  1.100
  libpostproc    58.  1.100 / 58.  1.100
[Parsed_loop_6 @ 0x6058b1b78c40] Number of frames to loop is not set!
[Parsed_loop_8 @ 0x6058b1b79240] Number of frames to loop is not set!
Input #0, image2, from '/tmp/vhs3282649779/frame-text-%05d.png':
  Duration: 00:07:01.12, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: png, rgba(pc, gbr/bt709/iec61966-2-1), 1044x837, 25 fps, 25 tbr, 25 tbn
Input #1, image2, from '/tmp/vhs3282649779/frame-cursor-%05d.png':
  Duration: 00:07:01.12, start: 0.000000, bitrate: N/A
  Stream #1:0: Video: png, rgba(pc, gbr/bt709/iec61966-2-1), 1044x837, 25 fps, 25 tbr, 25 tbn
Input #2, lavfi, from 'color=#171717:s=1200x1000':
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #2:0: Video: wrapped_avframe, yuv420p, 1200x1000 [SAR 1:1 DAR 6:5], 25 fps, 25 tbr, 25 tbn
Input #3, png_pipe, from '/tmp/vhs3282649779/bar.png':
  Duration: N/A, bitrate: N/A
  Stream #3:0: Video: png, rgb24(pc, gbr/unknown/unknown), 1200x1000, 25 fps, 25 tbr, 25 tbn
Input #4, png_pipe, from '/tmp/vhs3282649779/mask.png':
  Duration: N/A, bitrate: N/A
  Stream #4:0: Video: png, gray(pc, gbr/unknown/unknown), 1200x1000, 25 fps, 25 tbr, 25 tbn
Stream mapping:
  Stream #0:0 (png) -> overlay
  Stream #1:0 (png) -> overlay
  Stream #2:0 (wrapped_avframe) -> scale:default
  Stream #3:0 (png) -> loop:default
  Stream #4:0 (png) -> loop:default
  paletteuse:default -> Stream #0:0 (gif)
Press [q] to stop, [?] for help
[Parsed_loop_6 @ 0x706834019100] Number of frames to loop is not set!
[Parsed_loop_8 @ 0x7068340197c0] Number of frames to loop is not set!

Host your GIF on vhs.charm.sh: vhs publish <file>.gif

Desktop (please complete the following information):

• OS: Kubuntu 24.10
• Browser: chromium
• vhs version v0.9.0 (a5f09b2)

Additional context
Many thanks for this awesome program, I love it! :)

Commentary

Ok, I have extracted the precise ffmpeg commandline executed by vhs:

ffmpeg -y -r 50 -start_number 1 -i /tmp/vhs3763011057/frame-text-%05d.png -r 50 \
-start_number 1 -i /tmp/vhs3763011057/frame-cursor-%05d.png -f lavfi -i \
color=#171717:s=1200x1000 -i /tmp/vhs3763011057/bar.png -i /tmp/vhs3763011057/mask.png \
-filter_complex "[0][1]overlay[merged]; [merged]scale=1080:850:force_original_aspect_ratio=1[scaled]; 
[scaled]fps=50,setpts=PTS/1.000000[speed]; 
[speed]pad=1200:970:(ow-iw)/2:(oh-ih)/2:#29283b[padded]; 
[padded]fillborders=left=60:right=60:top=60:bottom=60:mode=fixed:color=#29283b[padded] ; 
[3]loop=-1[loopbar]; [loopbar][padded]overlay=0:30[withbar] ; 
[4]loop=-1[loopmask]; [withbar][loopmask]alphamerge[rounded] ; 
[2]scale=1200:1000[bg]; [bg][rounded]overlay=(W-w)/2:(H-h)/2:shortest=1[withbg] ; 
[withbg]split[plt_a][plt_b]; [plt_a]palettegen=max_colors=256[plt]; 
[plt_b][plt]paletteuse[palette]" -map "[palette]" demo.gif

I also saved the dir /tmp/vhs3763011057/ containing the png frame images away. Then I run the ffmpeg command myself which leads to the same error as above.

I also looked if the provided frame and cursor images matched - they did, that is, no image was missing. There were 14514 text and 14514 cursor frames.

[raphamorim]

Hey @TLINDEN thank you for the issue! I tried locally (by manual command trigger) it actually does warn that message but it doesn't break or anything for me. It actually creates the gif file.

I am using a slightly newer ffmpeg version (7.1) but I don't think it's related.

I tried the steps you sent but nothing really happens, could you help me if I am missing anything?

[raphamorim]

If I run over both tapes, it does works for me as well

[TLINDEN]

Well, in the meantime, I have splitted the tape file into two separate files, which is a workaround.

The failure only happens, if it's one large tape file. To reproduce, checkout this earlier commit: 140b312, there's only 1 tape file.

PS: sorry for posting this in the wrong repo!

[raphamorim]

The failure only happens, if it's one large tape file. To reproduce, checkout this earlier commit: 140b312, there's only 1 tape file.

Will give it a try! Thank you

PS: sorry for posting this in the wrong repo!

No worries at!! 🙏