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• flashsv2enc : fix prev-Z-prime encoding

  7 septembre 2012, par Michael Niedermayer

  flashsv2enc : fix prev-Z-prime encoding

• Ffmpeg hangs while transcoding HDHomerun Prime on channel change

  23 octobre 2017, par devo1929

  I’m using ffmpeg to transcode a live stream from a HDHomerun Prime. Everything is working beautifully. However, one ability that I would like, if possible, is the ability to change the channel on the HDHomerun without having to stop and restart the ffmpeg transcoding process.

  I start the ffmpeg process to begin reading the UDP feed from the HDHomerun. It writes the stream to a series of *.ts files with a m3u8 playlist.

  The second I use hdhomerun_config to change the channel on the device, ffmpeg immediately reports the following and hangs :

  [mpegts @ 0000018b4e05be60] New video stream 0:3 at pos:295211888 and DTS:40884.7s=108 drop=0 speed=1.02x
[mpegts @ 0000018b4e05be60] New audio stream 0:5 at pos:295279568 and DTS:40884.4s
frame= 4488 fps= 29 q=23.0 q=27.0 q=23.0 size=N/A time=00:02:28.94 bitrate=N/A dup=108 drop=0 speed=0.959x

  The command I am using to launch ffmpeg is :

  ffmpeg.exe -t 03:00:00 -i "udp://192.168.1.150:5000?fifo_size=1000000&overrun_nonfatal=1" -vf yadif=0:-1:1 -y -threads 4 -c:v libx264 -s 1280x720 -r 30 -b:v 4500k -force_key_frames expr:gte(t,n_forced*2) -profile:v high -preset fast -x264opts level=41 -c:a libfdk_aac -b:a 96k -ac 2 -hls_time 10 -hls_list_size 6 -hls_wrap 6 -hls_base_url /stream/ -hls_flags temp_file -hls_playlist_type event "C:\temp\streams\4500-stream.m3u8"

  Is there a specific command that I can pass to allow ffmpeg to "recover" from this ? Or, is there an arg that prevents this hang in the first place ? I’m using the latest version v3.4 of ffmpeg cross-compiled for Windows from Ubuntu. The issue also occurred using the stable version v3.4 of ffmpeg for Windows from ffmpeg.org.

  Edit :

  A new discovery to the issue, but still not yet resolved :
  If I change to the channel BACK to the original channel, Ffmpeg is able to continue writing the stream.

  Example : I start on channel X. Ffmpeg is recording to a file. I change to channel Y. Ffmpeg outputs a message similar to the one posted above and "hangs." I change back to channel X and ffmpeg picks up where it left off, no problem.

• ffmpeg blend=screen makes background look green or foreground green

  24 novembre 2022, par OneWorld

  When I apply a screen blend to the foreground asset (Pikachu) over the background asset (White circle on black background)
GIMP and Adobe Photoshop make the circle asset look white, and the background asset look RGB like this :-

  


  

  


  which is how it should look.

  


  However, if we take the input assets :-

and


  


  and use this ffmpeg command

  


  ffmpeg -i circle_rgb_50.png -i pikachu_rgb.png -filter_complex "[0:v][1:v]blend=screen" pikachu_screened_over_circle_rgb_just_blend.png


  


  we get this :-


  


  and if I reverse the blend so that the inputs to the blend function are the other way around, like this :-

  


  ffmpeg -i circle_rgb_50.png -i pikachu_rgb.png -filter_complex "[1:v][0:v]blend=screen" pikachu_screened_over_circle_rgb_just_blend_other_way_around.png


  


  we get this :-


  


  Why doesn't FFMPEG do blending the same way as GIMP or Adobe Photoshop ?

  


  Or is there another parameter I need to pass so that blends look as they should ?