adding silent audio in ffmpeg

Here's a command for the latest ffmpeg, works with MP4 (H264/AVC):

ffmpeg -f lavfi -i aevalsrc=0 -i input.mp4 -c:v copy -c:a aac -map 0 -map 1:v -shortest output.mp4

anullsrc audio filter

You can use ffmpeg to create the silent audio and combine it with a video in one step. This example will use the anullsrc audio filter to generate stereo silent audio with a sample rate of 44100:

ffmpeg -f lavfi -i anullsrc=channel_layout=stereo:sample_rate=44100 -i video.mov -c:v copy -c:a aac -shortest output.mov

• channel_layout=stereo:sample_rate=44100 is the default, but I included it just as an example of how to use these options.

Ignoring existing audio

If your video input file has audio that you want to ignore then use the -map option to override the default stream selection behavior:

ffmpeg -f lavfi -i anullsrc -i video.mov -c:v copy -c:a aac -map 0:a -map 1:v -shortest output.mp4

• -map 0:a -map 1:v can be translated as: from the first input (0) use the audio (a), and from the second input (1) use the video (v).

---

Notes

• These examples will stream copy the video so it does not get re-encoded (like a "copy and paste").

• It is always recommended to use a recent ffmpeg. Links to recent builds are on the FFmpeg Download page or you can refer to a step-by-step guide to compile ffmpeg.