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• How to run a video on chromium/lubuntu smoothly on a low-end machine ?

  29 juillet 2020, par Altuğ Ceylan

  the cpu of the machine is Atom X5-Z8350 with a ram size of 4 GB. It does not have an external gpu.
The problem is that when it runs a video on chromium such as a youtube video, it stutters and fps drop happens. I found out that the cpu supports h264 and vp8, and chromium only supports vp-8 and vp-9. Therefore, I used ffmpeg to transcode a video I downloaded from youtube to see if it was going to help.
I used the following script from my github repository which also contains driver update scripts etc

  


  
#$1 input filename
#$2 good realtime best
#$3 --cpu-used for best and good deadline valid values are from 0 to 5 for realtime 0 to 15
#$4 tile columns allow multi threading use powers of 2 eg 2=4
#$5 no threads to use
#$6 minrate around 2k is good for 1080p60
#$7 out filename
# -b:v bitrate 512k maybe too low for 720p30 try 1500k to 2000k 
#for fast/quality use realtime 6-7 
#for very good quality use good 2
start=$(date +%s.%N)
ffmpeg -i $1 -r 30 -g 90 -s 1280x720 -aspect 16:9 -c:v libvpx -deadline $2 -row-mt 1 -b:v 2500k -threads $5 -tile-columns $4 -cpu-used $3 -minrate $6 -bufsize 3000k -maxrate 3000k -crf 30 -frame-parallel 1 $7.webm
duration=$(echo "$(date +%s.%N) - $start" | bc)
execution_time=`printf "%.2f seconds" $duration`
echo "Script Execution Time: $execution_time"



  


  I changed crf to 5, -r to 120 -s to 1920x1080 and passed $2 as realtime, $3 as 7, $4 as 2 , $5 as 4, $6 as 2000k, I used the following video https://www.youtube.com/watch?v=jZKvJY6gDfg. It was a lot better than before, the chromium was having hard time running 720p30 but now it actually ran the 1080p120 video with minor tear and fps drops. How can I prevent the tears and the fps drops from happening ?

  


• Revision 3118aba32c : twopass_encoder.c : Silence MSVC data loss warnings. Use unsigned int instead of

  19 février 2014, par Tom Finegan

  Changed Paths :
   Modify /examples/twopass_encoder.c

  
  
  twopass_encoder.c : Silence MSVC data loss warnings.

  Use unsigned int instead of uint64_t for duration and deadline
  arguments to functions get_frame_stats() and encode_frame().

  Change-Id : I1f26a7afc38ae89916b2c67415ced26fdc9d53e7

• ffmpeg : drawtext fade in/out with zmq

  11 novembre 2019, par jb_alvarado

  There are several ways to fade in and out text in ffmpeg. But I only found solutions where the actual time is known.

  But what can I do, when I don’t know the current running time and I would like to fade in and out a text ?

  Let’s say I have an endless stream and I want to fade in a text with zmqsend. And the fade should start immediately. For that my understanding is, that I need to store some time information in a variable and calculate with that. But storing variables is not possible in ffmpeg expressions - right ?

  For testing purposes here are a playing instance :

  ffplay -dumpgraph 1 -f lavfi "color=s=512x288:c=black,zmq,drawtext=text=''"

  For adding some text with zmq I can run now :

  echo Parsed_drawtext_2 reinit text="Hello\ World,\ what’s\ up?" | zmqsend

  Or if I know the running time and after 10 seconds I want the text fade in :

  "text='Hello\ World':fontsize=:fontcolor=ffffff:alpha='if(lt(t,10),0,if(lt(t,11),(t-10)/1,if(lt(t,16),1,if(lt(t,17),(1-(t-16))/1,0))))'"

  My goal is now to have an expression what I can send, so that ffmpeg starts fading in the text and out after a certain time.

  Something like :

  now=t,if(lt(t,now+10),0,if(lt(t,now+11),(t-(now+10))/1,if(lt(t,now+16),1,if(lt(t,now+17),(1-(t-(now+16)))/1,0))))

  Is there a way to store variables in expression, or is there any other way to realize this ?