Doing P7 to P8.1 conversion on the fly using pipes (no temporary files)

[suyash192]

This might not be exactly the responsibility of this tool, but I would really appreciate it if you could help me with this.

I have successfully converted P7 to P8.1 using ffmpeg, dovi_tool and mkvmerge but with using temporary files. Now, I need to do the same on the fly using pipes instead of temporary files as I'm trying to create an http transcoding service for streaming videos.

dovi_tool doesn't support stdout output but I can use named pipes for that (mkfifo), so that problem is solved.

mkfifo /tmp/named_pipe.hevc

ffmpeg -i original.mkv -c:v copy -bsf:v hevc_mp4toannexb -f hevc - | dovi_tool -m 2 convert --discard - -o /tmp/named_pipe.hevc

But Mkvmerge doesn't support reading from pipes and has stated in their Wiki that they do not intend to support it as well, so that leaves me with no option but to use ffmpeg for muxing.

With ffmpeg I'm trying to mux using this command

ffmpeg \
  -fflags +genpts \
  -f hevc -i /tmp/named_pipe.hevc \             # the video stream from a separate ffmpeg -> dovi_tool process
  -i original.mkv \
  -map 0:v:0 \
  -map 1:a:0 \
  -c:v copy \
  -c:a copy \
  -f matroska -                                 # output to stdout

but it's giving me the below error

matroska @ 0xa56c40a00] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
[matroska @ 0xa56c40a00] Can't write packet with unknown timestamp

Do you have any idea how I can generate these timestamps in the entire pipeline? I have added -fflags +genpts but it does not look to do anything.

[quietvoid]

Not the place to ask for FFmpeg questions.

[quietvoid]

No idea.

[suyash192]

At least any chance for dovi_tool to give output to stdout? To make things simpler for people like me.

[quietvoid]

It's not supported and most likely won't be.

[suyash192]

Any reason why it wont be?

[quietvoid]

Because it's not a feature I have a use for and it requires time to develop.
Pull requests welcome.