ffmpeg on a Raspberry Pi - Help Required!
Posted: Sat Nov 25, 2017 9:11 pm
Hi
The Short Version
I'm using ffmpeg on a RPi3 to generate an H264 transport stream using either libx264 or h264_omx and mpegts. I can get it to work properly with libx264, but the CPU is maxed out. With h264_omx it appears to work, but the resulting TS has an undefined frame rate. VLC will play the TS, but it is unsuitable for transmission using the DVB-S standard. I know that h264_omx is at least functioning, because it works with flv output.
I realise that this a very specialist question and I am not expecting answers - just pointers to where I might find any more information on how to force mpegts to define the frame rate. Google has not been helpful!
Dave
The Long Version
This code to produce a web stream using ffmpeg, libx264 and flv works well but maxes out the CPU:
Using omx_h264 in this application also works well with much lower CPU usage:
So moving on to using mpegts output format. This code works, but maxes out the CPU cores:
videots is a fifo that is read by another application that converts the transport stream into I and Q signals for a DVB-S TV transmission.
If I substitute h264_omx for libx264, it runs with lower CPU usage, but produces a non-compliant transport stream with a (video) frame rate undefined:
I have taken the audio codec out of the examples above for clarity. When the audio codec was present, I could decode the audio from the stream.
I also tested with writing the output to a .ts file and using Promax TS Analyser software to look at the stream properties. It said that the (video) frame rate in the h264_omx stream was 0.0 fps. VLC played both files OK, but when checking codec properties, there was no entry for the frame rate in the h264_omx-produced file. In the libx264 file the frame rate was correctly described as 25.0 fps. I think that this is the reason it does not work in my application - so I am looking for a way to make mpegts define the (video) frame rate.
Here is my ffmpeg configuration:
I have played with trying to define a frame rate in just about everywhere in the ffmpeg statement. I'm about to give up on this, but just wondered if anyone had seen anything like it before.
The software is intended to be an enhancement to the Portsdown Transmitter: https://wiki.batc.tv/The_Portsdown_Transmitter The existing code is on GitHub here: https://github.com/BritishAmateurTelevisionClub/rpidatv
Thanks in advance
Dave
The Short Version
I'm using ffmpeg on a RPi3 to generate an H264 transport stream using either libx264 or h264_omx and mpegts. I can get it to work properly with libx264, but the CPU is maxed out. With h264_omx it appears to work, but the resulting TS has an undefined frame rate. VLC will play the TS, but it is unsuitable for transmission using the DVB-S standard. I know that h264_omx is at least functioning, because it works with flv output.
I realise that this a very specialist question and I am not expecting answers - just pointers to where I might find any more information on how to force mpegts to define the frame rate. Google has not been helpful!
Dave
The Long Version
This code to produce a web stream using ffmpeg, libx264 and flv works well but maxes out the CPU:
Code: Select all
/home/pi/rpidatv/bin/ffmpeg \
-f v4l2 -input_format h264 \
-i /dev/video0 -thread_queue_size 2048 \
-f alsa -ac 1 -ar 44100 \
-i hw:1,0 \
-framerate 15 -video_size 720x576 -c:v libx264 -b:v 512k -minrate:v 512k -maxrate:v 512k \
-b:a 22050 -ac 1 \
-g 25 \
-f flv rtmp://sitename.org.uk/live/keykey &Code: Select all
/home/pi/rpidatv/bin/ffmpeg \
-f v4l2 -input_format h264 \
-i /dev/video0 -thread_queue_size 2048 \
-f alsa -ac 1 -ar 44100 \
-i hw:1,0 \
-framerate 15 -video_size 720x576 -c:v h264_omx -b:v 512k -minrate:v 512k -maxrate:v 512k \
-b:a 22050 -ac 1 \
-g 25 \
-f flv rtmp://sitename.org.uk/live/keykey &Code: Select all
/home/pi/rpidatv/bin/ffmpeg -loglevel debug \
-f image2 -loop 1 -pix_fmt yuv420p\
-framerate 25 -pix_fmt yuv420p \
-i /home/pi/rpidatv/video/tcf.jpg \
-c:v libx264 -pix_fmt yuv420p \
-b:v 320600 -minrate:v 320600 -maxrate:v 320600 \
-f mpegts -blocksize 1880 \
-mpegts_original_network_id 1 -mpegts_transport_stream_id 1 \
-mpegts_pmt_start_pid 4095 -streamid 0:256 -streamid 1:257 \
-metadata service_provider=G8GKQ -metadata service_name=G8GKQ \
-muxrate 1382352 -y videots &
If I substitute h264_omx for libx264, it runs with lower CPU usage, but produces a non-compliant transport stream with a (video) frame rate undefined:
Code: Select all
/home/pi/rpidatv/bin/ffmpeg -loglevel debug \
-f image2 -loop 1 -pix_fmt yuv420p\
-framerate 25 -pix_fmt yuv420p \
-i /home/pi/rpidatv/video/tcf.jpg \
-c:v h264_omx -pix_fmt yuv420p \
-b:v 320600 -minrate:v 320600 -maxrate:v 320600 \
-f mpegts -blocksize 1880 \
-mpegts_original_network_id 1 -mpegts_transport_stream_id 1 \
-mpegts_pmt_start_pid 4095 -streamid 0:256 -streamid 1:257 \
-metadata service_provider=G8GKQ -metadata service_name=G8GKQ \
-muxrate 1382352 -y videots &
I also tested with writing the output to a .ts file and using Promax TS Analyser software to look at the stream properties. It said that the (video) frame rate in the h264_omx stream was 0.0 fps. VLC played both files OK, but when checking codec properties, there was no entry for the frame rate in the h264_omx-produced file. In the libx264 file the frame rate was correctly described as 25.0 fps. I think that this is the reason it does not work in my application - so I am looking for a way to make mpegts define the (video) frame rate.
Here is my ffmpeg configuration:
Code: Select all
ffmpeg version 3.3.2 Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 4.9.2 (Raspbian 4.9.2-10)
configuration: --prefix=/home/pi/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/pi/ffmpeg_build/include --extra-ldflags=-L/home/pi/ffmpeg_build/lib --enable-gpl --enable-libfreetype --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-nonfree --enable-mmal --enable-omx --enable-omx-rpi
libavutil 55. 58.100 / 55. 58.100
libavcodec 57. 89.100 / 57. 89.100
libavformat 57. 71.100 / 57. 71.100
libavdevice 57. 6.100 / 57. 6.100
libavfilter 6. 82.100 / 6. 82.100
libswscale 4. 6.100 / 4. 6.100
libswresample 2. 7.100 / 2. 7.100
libpostproc 54. 5.100 / 54. 5.100
The software is intended to be an enhancement to the Portsdown Transmitter: https://wiki.batc.tv/The_Portsdown_Transmitter The existing code is on GitHub here: https://github.com/BritishAmateurTelevisionClub/rpidatv
Thanks in advance
Dave