Questions about transcoding video with audio and subtitle passthrough using MKV files

Toby Widdows toby at
Thu Mar 4 20:23:03 UTC 2021


I am by no means a developer, and I have struggled to get my head around gstreamer.  I have what on the face of seems like a simple issue and one which I have achieved with FFMPEG and some linux scripting, however I have a jetson nano that i want to use for this, and the FFMPEG someone has built to support the nvidia encoders and decoders gives me weird video issues, and as the nvidia forums promote gstreamer, I thought I would give this a go..

I have video in MKV containers in H264 video format with multiple audio and multiple subtitle tracks.  I want to be able to transcode the video, and passthrough all the audio and subtitle tracks into a new MKV file.

I have figured out how to do the video, but can not get my head around the methods needed to do the audio and subtitle tracks.

I can discover how many audio and subtitle tracks there are and can build a script around all this, if I could only just figure out the syntax for gst-launch.  

Help much appreciated.  

And apologies in advance for the series of stupid questions that may come out of this thread 

this is my starting point  :-

gst-launch-1.0 filesrc location=./2.mkv \
! matroskademux \
! h264parse \
! nvv4l2decoder \
! nvv4l2h265enc bitrate=2000000 \
! h265parse \
! matroskamux \
! progressreport update-freq=1  \
! filesink location=./new2.mkv  

Thanks again in advance

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