ffmpeg map first video and audio multiple

Itsoffset applies to both streams of a file, and we use “map” to split out the stream we want to change. If the audio is off by 1 second, you might type -itsoffset 1.0 (or -itsoffset 00:00:01.0000). “Itsoffset” is used with a specific amount of time that you want to apply to a file. “-map 1:1” means second input file and stream 1 (audio) “-map 1:0” means second input file and stream 0 (video) “-map 0:1” means first input file mentioned on the command-line and its stream 1 (audio) The input file number will be 0 or 1, and stream will be 0 (video) or 1 (audio)Īn important side note on file numbering with ffmpeg: 0 is the first, 1 is the second Here is a picture to better clarify the description (click pic for better view): First I will demonstrate the syntax of the “map” and “itsoffset” switches and what they mean.

There are a few different ways to accomplish the same result with minor variations, and I will try to demonstrate them. We will use itsoffset and map to delay one of the streams, and then merge them back together into another file. We will use this one input file twice, once for its audio portion, and once for its video portion. The itsoffset switch is nearly always used in conjunction with the “map” switch, since this tells ffmpeg which stream you want to affect, and what streams you wish to merge into a new output file.įor our purposes, we will deal with just one input file that has two streams out of sync (the most common problem). But sometimes during a conversion to another file format (such as mp4), the audio and video will not remain in sync and the itsoffset switch can be used to adjust them. On my camera, they merge into an MTS high-def formatted file. A typical video camera will record one video stream and one audio stream which are merged into one file. The itsoffset switch is used to nudge (forward or backward) the start time of either an audio or video “stream”. It will take some time to learn, but is very powerful once you understand it.

I will try to explain how to use a couple of these switches to correct common sync problems with videos. Some of them are not explained very well in the documentation, and many websites have confusing postings by well-meaning people trying to make use of the switches. The ffmpeg program has numerous “switches” that help to adjust and convert audio and video files.

Ffmpeg map first video and audio multiple