Input from STDIN and spooling through audio/video.

[Demonstrandum]

Take input from STDIN from a pipe

I was wondering if piping the video data directly to mkchromecast through stdin would be possible.
e.g. data from the webcam:

ffmpeg -loglevel panic -f video4linux2 -i /dev/video0 -f ogg - | mkchromecast --video -
# The dash at the end in the ffmpeg command means it outputs to 
# STDOUT instead of to a file,
# and the dash in the mkchromecast command would mean it read
# the data from STDIN.

I couldn't find an way of doing this, so instead I recorded it to a separate file with

ffmpeg -f video4linux2 -i /dev/video0 -f ogg me.ogg

then in a separate shell session I streamed it:

mkchromecast --video me.ogg

which of course results in a huge delay as it reads form the beginning of the file, and the beginning was mkchromecast connecting.

This brings me on to my next question:

Spooling

Is there any way to spool backwards and forwards from whatever file it's reading, perhaps a way to go back to the beginning of the file or go to the very end (useful for streaming continuously growing file like from a webcam).

I don't know if any of this seems reasonable.

[muammar]

I will try to put something together, but I am more than happy to receive a PR if you want to.

[muammar]

@Demonstrandum I have pushed fbae38e, can you check the devel branch and let me know if it works? The example you showed here should work in the following way:

python3 mkchromecast.py --video --command 'ffmpeg -f video4linux2 -i /dev/video0 -f ogg pipe:1'

[Demonstrandum]

Hi, it might just be me but it doesn't seem to completely work. It even goes so far as to say it's streaming and I see a loading animation on the TV however it stops and then goes back to the default casting logo home screen.

I know streaming with seekable formats like mp3 is difficult and I was using ogg, so I set it to ogg for audio coding with the command:

python mkchromecast.py -c ogg --video --command 'ffmpeg -f video4linux2 -i /dev/video0 -f ogg pipe:1'

But yet it did not work.

One thing I saw when trying was the line:

The media type string used is: video/mp4

The video format should be ogg, how can I change this?

[muammar]

Chromecast does not support ogg for video. Check this: https://developers.google.com/cast/docs/media. Could you try mp4 and let me know if it works? if it does, then I can update the documentation. Thanks.

[Demonstrandum]

Trying with mp4 for the -f flag doesn't seem to work either. Does this work for you?

[muammar]

Trying with mp4 for the -f flag doesn't seem to work either. Does this work for you?

I will try this again, you are right that it is not working. I will get back to you. Thanks for being so responsive.

[muammar]

@Demonstrandum I have made a test. This is working for me:

python3 mkchromecast.py --video --command 'ffmpeg -re -i /path/to/myvideo.mp4 -map_chapters -1 -vcodec libx264 -preset ultrafast -tune zerolatency -maxrate 10000k -bufsize 20000k -pix_fmt yuv420p -g 60 -f mp4 -max_muxing_queue_size 9999 -movflags frag_keyframe+empty_moov pipe:1' 

The small flag that I implemented is working when I use the command above. This means that one has to find the right " ffmpeg command" that can be used to pipe correctly. I will let you know if I find how (you do the same if you can please). Then we can proceed to modify the documentation accordingly.

[muammar]

@Demonstrandum did it work for you?

[jlherren]

Any comment on the second part of the question about being able to seek within the video? I understand that jumping around in the video stream is non-trivial if the video is being transcoded/encoded on the fly. But given a H.264/AAC file which the chromecast can play natively it probably shouldn't be too hard. (Seeking would usually happen from the Google Home app.)

[Demonstrandum]

@muammar Sorry for the slightly late response, but, no I can't seem to get it to work.
I see a little loading animation on the TV and nothing happens. I also tried the webcam stream through ffmpeg with the --command as well, but the webcam light only flashes on for a brief moment(?), turns off and nothing happens.

😞