![]() ![]() Since the normal goal is to use movies in a listening experiment, we usually want to avoid making unintentional changes to the audio channels when processing video files. Many compressed video outputs will also include compressed audio by default. Note that the video image will be stretched horizontally or vertically if the output width/height ratio is different from the ratio in the input file. Select the output video resolution with the video filter parameter: Set -q 2 to get a pretty high quality video bitrate. ![]() The -q parameter can also be used to control the quality of the video output. vcodec copy # for all versions of ffmpeg c:v copy # for newer versions of ffmpeg only This will override any encoding-related settings. Unfortunately, this parameter is not available in older versions of ffmpeg you can use -vcodec copy to copy over the video from the original file without re-encoding it. Set it closer to the original file's bitrate to reduce the amount of compression. Add this argument somewhere in the command, set off by spaces-for example, right before specifying the output file. Set the bitrate of the output file with the -b:v argument. To extract only the audio portion of a video, use the -vn parameter to indicate no video output: Using a small GOP value in step one makes this quick jump possible:įfmpeg -ss target-1 -i temp.MXF -ss 1 -q 2 -t duration_of_chunk out.mpg Here's one strategy for extracting video from MXF files that has worked:ġ) convert to a format that has a small GOP (group of pictures) value -g 1Īnd keep a high video bit rate ( -b:v) to keep detail in the video:įfmpeg -i my.MXF -g 1 -b:v 35000k temp.MXFĢ) seek in the temp.MXF file to just before your target start time for the extracted video - the first seek (ss) in this command jumps to 1 second before the target very quickly and the second seek steps over frames until it gets to exactly your target time. This command, for example, would extract a 1.5-second clip starting at 5.3 seconds into 'longfile.avi' and save it to 'shortfile.avi':įfmpeg -ss 00:00:05.30 longfile.avi -t 1.5 shortfile.avi To extract video from a certain time, use the -ss and -t flags to specify start time and duration, respectively:įfmpeg -ss HH:MM:SS INFILE -t DURATION OUTFILE 4 Changing the video resolution (scaling).
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