Newest 'ffmpeg' Questions - Stack Overflow

Les articles publiés sur le site

• how to improve quality with ffmpeg flv [closed]

  14 novembre 2013, par user692601

  i'm haveing problem when converting movies to FLV, i get a lot of small squares in the picture. maybe someone know why? and how i can remove those squares and make picture better? my code is:

  ffmpeg -i movie.mp4 -f mpegts -acodec libmp3lame -ar 48000 -ab 128k -s 320.240 -vcodec libx264 -b 320k -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -subq 7 -trellis 1 -refs 1 -coder 0 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -bt 200k -maxrate 10M -bufsize 10M -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 -g 30 -async 2 out.flv

  thanks!

• Ffmpeg & PHP - Small Clip with Good Quality

  14 novembre 2013, par FakeHeal

  what are the best options to keep video in nearly good quality while converting it to flv and shrinking its size?

  I use the followin code now:

  exec("ffmpeg -i $faila -sameq -s 600x450  -ar 44100 $file_final");
  

• ffmpeg setting for HD and normal quality

  14 novembre 2013, par gabo84

  Hello i need to have two versions of the same file stored on my server, medium and HD quality, the thing is that don't really know ffmpeg that well so im just trying this is code at random, i'm using the code belo but I end up with a much larger file, however it works,it plays.

  ffmpeg -i inputfile.wmv  -vcodec libx264 -ar 44100 -b 200 -ab 56 -crf 22 -s 360x288 -vpre medium -f flv tmp.flv
  

  Just need the two commands to create the 2 different files

• Do FFMPEG H264 compression presets affect the video quality ? [closed]

  14 novembre 2013, par angainor

  I am definitely not an FFMPEG expert, but according to this document:

  A preset is a collection of options that will provide a certain encoding speed to compression ratio. A slower preset will provide better compression (compression is quality per filesize). General usage is to use the slowest preset that you have patience for. Current presets in descending order of speed are: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow, placebo.

  So as I understand it, the ffmpeg presets should not affect the quality of the output video, but should only determine the compression ratio / output file size. Consequently, assuming the same quality setting (I will use -crf 24), the files should be larger for e.g., faster preset than for the slower preset. That would be the only reason to use a slower preset - to get a smaller file size.

  This turns out not to be the case. I encode a HD stream from a handycam using different presets, everything else is the same:

  ffmpeg -y -i "$fname" -vf yadif=1,scale=-1:720 -acodec aac -ab 128k -ac 2 -strict experimental -vcodec libx264 -vpre slow -threads 2 -crf 24 "$outp"
  

  Surprisingly, I get the smallest file size for veryfast preset! For example:

  • slower: output bitrate 3500kbps, encoding speed 17 fps, file size 29MB
  • veryfast: output bitrate 3050kbps, encoding speed 34 fps, file size 25MB

  Which I think is not as it should be. Now I wonder, is that due to a worse encoding quality for the veryfast preset? Or in my case using slower does simply not make sense for some reason?

• Avconv file not saved while recording video stream

  14 novembre 2013, par narutov6

  I'm trying to record a video from an external RCA camera and a usb webcam.

  /dev/video0 -> logitech webcam

  /dev/video1 -> external camera plugged in through a RCA-to-Usb adapter.

  when I use the following avconv command using the video from the webcam

  avconv -f video4linux2 -r 24 -s 640x480 -i /dev/video0 video.avi

  or using the external camera

  avconv -f video4linux2 -s 720x480 -i /dev/video1 video.avi
  

  the program starts correctly without errors. Then I press Ctrl+C to stop recording. But there is no video.avi file in the current directory.

  Do you have any advice?

  Note: I'm able to visualize the video stream coming from both the webcam and the external camera with vlc using:

  vlc v4l2:///dev/video1          and           vlc v4l2:///dev/video0