Feature Request: Start ffplay in paused mode

[geegee]

I would like to request the addition of a global option for ffplay, called something like -start_paused, which will normally open the input but pause on the first frame until the pause key (space in ffplay) is pressed again, or the 's' key is pressed to advance and pause on the next frame.

This would be very useful for viewing CBZ and CBR files, which are nothing but ZIP and RAR files, respectively, with different extension names and which contain a collection of picture files such as .jpg, .bmp, gif, and png.

The current problem is that opening such zip/rar files directly with ffmpeg/ffplay, to the best of my knowledge, isn't supported. Thus, something like the following command can be used to circumvent this limitation and to allow viewing all compressed pictures in ffplay, which pipes extracted files to ffplay:

7z e -so input.zip | ffplay -hide_banner -infbuf -fs -i pipe:

The problem with the approach above is that ffplay will display the contents at 25 fps, with each frame being one picture file from the compressed archive. Thus, manual pausing (or the 's' key) needs to be used to control how fast ffplay displays each frame. Using manual pause is also imperfect because, typically, human reaction will be too slow to pause right on the first frame, and thus a few initial frames will have been displayed too fast. On top of that, the ability to rewind or seek to previous frames is not possible with this command.

Therefore, once again, my proposed solution would be to add a global option for ffplay, called something like -start_paused, which will normally open the input but pause on the first frame until the pause key (space in ffplay) is pressed again or the 's' key is pressed to advance and pause on the next frame.

The problem of not being able to go to the previous frame or rewind to the very first frame would still remain, but this seems to be a problem with how piping works. A further solution to that would be to also introduce a way to buffer input frames, I tried to achieve this using -infbuf but that did not seem to change anything regarding seeking past frames.

While I was experimenting with possible solutions, I noticed that ffplay will sometimes be able to read directly from zip files to my very own surprise, but with some limitations it seems. For example, ffplay -i file.zip surprisingly works as long as the contents are .jpg files, but will fail if the contents are .png (-loglevel trace seems to indicate that ffplay tries to open .png's in the .zip file as mp3's instead of png_pipe). Thus, I worked around this by using the piping command I mentioned previously, but that came at the cost of losing the ability of seeking previous frames with the arrow keys.

Thank you very much for considering my suggestion and the amazing work you do!