ffmpeg HIGH cpu usage while streaming

kzo81 · 10-22-2019, 01:15 AM

Hi Folks,

I have a streaming and recording script for an embedded ARM7 SoC. It's done under Yocto Project. The issue is the intense CPU usage around 97-100% for 1 core out of 4. Do you have any idea how could I distribute the streaming task over the 4 cores? I've been testing with -threads 4 ffmpeg option, with not much success. I double checked the Yocto recipie file, and ffmpeg was compiled with multi threading feature and to arm7 architecture.

here is the script:

Code:

#!/bin/bash

if [ ! -e $(uci get application.audio.ffserver_config) ];then
cat > $(uci get application.audio.ffserver_config) <<EOF

HTTPPort $(uci get application.audio.streaming_port)
HTTPBindAddress 0.0.0.0
MaxHTTPConnections $(uci get application.audio.max_http_conns)
MaxClients $(uci get application.audio.max_clients)
MaxBandwidth $(uci get application.audio.max_bandwidth)
CustomLog $(uci get application.audio.ffserver_log)

<Feed audio.ffm>
        File /tmp/audio.ffm
        FileMaxSize 32M
</Feed>

<Stream audio>
	Feed audio.ffm
        Format wav
        AudioCodec pcm_s16le
        AudioBitRate 256
        AudioChannels 2
        AudioSampleRate $(uci get application.audio.streaming_sample)
        NoVideo
        StartSendOnKey
</Stream>

<Stream stat.html>
        Format status
</Stream>
EOF
fi
#
ffserver -f $(uci get application.audio.ffserver_config) &
#
sleep 1

mkdir -p $(uci get application.audio.recording_path) || exit 1

mkdir -p $(uci get application.audio.recording_path)/$(date '+%Y-%m-%d') || exit 1

ffmpeg -f alsa -i hw:0,0 -acodec pcm_s16le -f segment -strftime 1 -segment_time $(uci get application.audio.duration) -segment_format wav -ar $(uci get application.audio.recording_sample) $(uci get application.audio.recording_path)/$(date '+%Y-%m-%d')/%Y-%m-%d__%H_%M_$(uci get application.audio.recording_sample)_$(sed 's/://g' /sys/class/net/eth0/address).wav -shortest http://localhost:$(uci get application.audio.streaming_port)/audio.ffm

ondoho · 10-22-2019, 05:33 AM

Quote:

Originally Posted by kzo81

I've been testing with -threads 4 ffmpeg option, with not much success.

That's not a valid statement.
Please do some troubleshooting, see if you can tickle ffmpeg to tell you why it doesn't do as you told it.

Firerat · 10-22-2019, 05:49 AM

if it is the one thread that is high cpu then it will be bound to the one cpu

I guess the scheduler could share the load, but I imagine that will just switch through the cores

I wouldn't expect wav encoding to be cpu intensive, but I have no idea what that SoC is

you could try adding audio bitrate/samplerate to the ffmpeg
I'm not certain if the application.audio.ffserver_config influences ffmpeg or if it just provides metadata to client

kzo81 · 10-23-2019, 02:39 AM

Quote:

Originally Posted by ondoho

That's not a valid statement.
Please do some troubleshooting, see if you can tickle ffmpeg to tell you why it doesn't do as you told it.

Yes, you're right. I meant that I was debugging with inserting the -threads 4 to several places in the ffmpeg line, just after the -i option, before it, etc.
I seems it does not have any effect on how ffmpeg works internally.

Here it is:

Code:

ffmpeg -f alsa -i hw:0,0 -threads 4 -acodec pcm_s16le -f segment -strftime 1 -segment_time 300 -segment_format wav -ar 48000 /home/$USER/rec/$(date '+%Y-%m-%d')/%Y-%m-%d__%H_%M_.wav -shortest http://localhost:1234/audio.ffm

ffmpeg -f alsa -i hw:0,0 -acodec pcm_s16le -f segment -strftime 1 -segment_time 300 -segment_format wav -ar 48000 -threads 4 /home/$USER/rec/$(date '+%Y-%m-%d')/%Y-%m-%d__%H_%M_.wav -shortest http://localhost:1234/audio.ffm

ffmpeg -f alsa -i hw:0,0 -acodec pcm_s16le -threads 4 -f segment -strftime 1 -segment_time 300 -segment_format wav -ar 48000 /home/$USER/rec/$(date '+%Y-%m-%d')/%Y-%m-%d__%H_%M_.wav -shortest http://localhost:1234/audio.ffm

kzo81 · 10-23-2019, 02:45 AM

no effect how the initial sample rate is set.