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• FFmpeg - How to trim with high precision ?

  11 octobre 2016, par DSalenga

  I am pretty stucked with the way that FFmpeg trims videos, so I would be really grateful if someone could help me.
  Basically, what I am trying to do is : I have a video sequence and I want it to stop in a certain second, freeze the image some seconds (like a pause), and then reproduce again from the same exact frame. I could say that I am dealing with three videos : A.mp4 (first part of the video sequence), B.mp4 (frozen image) and C.mp4 (second part of the video sequence). Besides, I also perform an overlay with filter_complex.

  The part of generating a video from a static image is not a problem, my main concern is to find the way to trim and concatenate videos accurately. From other posts and sources, I discovered that FFmpeg trims from those Frames that are Keyframes, which can be forced. However, the result I obtain is not the appropriate one, because my video A ends in a frame different from the one in the beginning of C.

  The commands I am using are the following ones :

  ffmpeg -y -i VideoSequence.mp4 -c:v libx264 -pix_fmt yuv420p \
  
  -force_key_frames "expr: gte(t,n_forced * 15)" -t 30 VideoOut.mp4

  [Note that everything inside Filter Complex is about an Overlay, which works fine]

  As far as I know, the resulting video should have a Keyframe every 15 seconds. Now, I want to cut the video into 2 parts ("before second 15" and "after second 15") :

  ffmpeg -y -ss 00:00:01 -i VideoOut.mp4 -t 14 -c copy A.mp4
  
  
  
  ffmpeg -y -ss 00:00:15 -i VideoOut.mp4 -t 5 -c copy C.mp4 

  As mentioned, I expect the end of A.mp4 to "match" with the beginning of C.mp4 (at a frame precision), but the result I obtain is far from being perfect.

  Thank you very much, any kind of help will be appreciated !

• Generating High Quality Video from Images with Audio and Transistions(C#)

  18 octobre 2016, par M Imtiaz

  I am Making a Windows Application to Create a Video from a set of Images, also i want to add Audio and Transition Affects.
  i have searched Over the Internet and Found Some Libraries Like
  AForge.NET(FFMPEG Based), Splicer(https://splicer.codeplex.com/) and FFMPEG itself Command Based here.

  i am able to create video using all of the above libraries but these have certain limitations or may be i dont know the usage
  like

  1) AForge.Video.FFMPEG can create Video but there is no Option to add Audio

  2) FFMPEG Command Based can create Video from Images along with audio but Transitions found were only Fade In, Fade out(http://www.bogotobogo.com/FFMpeg/ffmpeg_fade_in_fade_out_transitions_effects_filters.php)

  3) Splicer.dll is working well it has All the Options for Adding Transitions and Audio but the quality of Video is not satisfactory.

  Now My Questions is how i can achieve my desired quality video along with Transitions and Audio from a set of Images.
  Thank you

• ffmpeg : Very High Frame Rate Values with -r option

  19 octobre 2016, par HewwoCraziness

  Please don’t mark this as a duplicate just because it mentions "ffmpeg frame rate". My question is not just a simple "How do I set the frame rate ?"

  I have set the output framerate of my video to a standard 30fps using the -r option, however, FFMPEG’s output values are closer to 250 for some reason.

  Here’s my syntax : ffmpeg.exe -y -i "C:\some\long\path.mp4" -f mp4 -r "30" -vcodec libx264 -preset slow -filter:v scale=320:240 -b:v 1000k  -aspect 16:9 -flags +loop -cmp chroma -b:v 1250k -maxrate 1500k -bufsize 4M -bt 256k -refs 1 -bf 3 -coder 1 -me_method umh -me_range 16 -subq 7 -partitions +parti4x4+parti8x8+partp8x8+partb8x8 -g 250 -keyint_min 25 -level 30 -qmin 10 -qmax 51 -qcomp 0.6 -trellis 2 -sc_threshold 40 -i_qfactor 0.71 -acodec libvo_aacenc -b:a 112k -ar 48000 -ac 2  "C:\some\long\path-output.mp4"

  Note the -r "30" on the first line.

  Thanks,

  HewwoCraziness