How to merge audio and video file in ffmpeg

Question

I want to merge an audio file (.wav or .au format) with a video file (.mp4 format).

Please suggest me how to achieve this. I want to merge these file to new .mp4 video file. An ffmpeg command would be very welcome.

Answer 1

Merging video and audio, with audio re-encoding

See this example, taken from this blog entry but updated for newer syntax. It should be something to the effect of:

ffmpeg -i video.mp4 -i audio.wav -c:v copy -c:a aac output.mp4

Here, we assume that the video file does not contain any audio stream yet, and that you want to have the same output format (here, MP4) as the input format.

The above command transcodes the audio, since MP4s cannot carry PCM audio streams. You can use any other desired audio codec if you want. See the FFmpeg Wiki: AAC Encoding Guide for more info.

If your audio or video stream is longer, you can add the -shortest option so that ffmpeg will stop encoding once one file ends.

Copying the audio without re-encoding

If your output container can handle (almost) any codec – like MKV – then you can simply copy both audio and video streams:

ffmpeg -i video.mp4 -i audio.wav -c copy output.mkv

Replacing audio stream

If your input video already contains audio, and you want to replace it, you need to tell ffmpeg which audio stream to take:

ffmpeg -i video.mp4 -i audio.wav -c:v copy -c:a aac -map 0:v:0 -map 1:a:0 output.mp4

The -map option makes ffmpeg only use the first video stream from the first input and the first audio stream from the second input for the output file.

Answer 2

Since I am not allowed to write comments to the first answer with my reputation, an addendum here, because I had this problem when encoding webms.
If your audio stream is for example longer than the video stream, you have to cut it or otherwise you will have the last video frame as a still image and audio running.

To cut either stream, you can use -ss [hh:mm:ss] -t [ss] before each of the -i "file.ext".
-ss [...] will define the starting point to cut
-t [...] will define the length of the segment in seconds

Example:

ffmpeg.exe -ss 00:00:10  -t 5 -i "video.mp4" -ss 0:00:01 -t 5 -i "music.m4a" -map 0:v:0 -map 1:a:0 -y out.mp4

Answer 3

Open command promt (windows+R -> Cmd+Enter). Then go to inside the folder where you have audio and video file. Apply this command:

ffmpeg -i "videoFile.mp4" -i "audioFile.mp3" -shortest outPutFile.mp4

You will get a new file named outPutFile.mp4 (a merged file of audio and video)

Answer 4

This worked for me:

ffmpeg.exe -i AudioT.m4a -i VideoT.mp4 -acodec copy -vcodec copy muxed.mp4

Answer 5

Try using mencoder (Yes it is ffmpeg based, but you never know). I use the -audiofile argument. I generally use ffmpeg, though, so take this advice with a pinch of salt.

And, if you use Windows, Mediacoder (not open source anymore sadly) works... its basically a frontend for a lot of gnu encoders and a few non-free ones.

Answer 6

In case one would like to merge audio and video with different length and also to apply Fade In and Fade Out the following worked for me:

ffmpeg -i Video001.mp4 -i Audio001.mp3 -af afade=t=in:st=0:d=3,afade=t=out:st=47:d=4 -c:v copy -c:a aac -shortest Output.mp4

In my case above the video was of length 51 so I chose Fade In of length 3 [Sec] and Fade Out* of ~4 [Sec]. Since fading is applied by a filter it required transcoding of the audio. In the case above I chose aac encoding.

The answer is heavily based on the answer of @PatrickGeorgi.

Answer 7

I've made a Python script to do this, you can try it if you want. Get it on github: https://github.com/mmakarov/replicator

Or look at video here: https://www.youtube.com/watch?v=4Uu1hS3-eQM

Replicator is a Python script to merge a few video files, transparent overlay, text areas with mp3 audio track. Final video will be exact same length as your audio track. Lenght of your video will be calculated automatically.

I've make this script in a try to merge any video sequence files with PNG transparent overlay, adding text areas on video, with mp3 audio track. Resulting video file are ready to upload on Youtube or any other video hosting services.

You can change it on your taste.

How to use it: 0. Open terminal and enter: git clone https://github.com/mmakarov/replicato...

1. Put your video files to project directory as 'source1.mp4', 'source2.mp4', etc
2. Put your PNG transparent image to project directory as 'overlay.png'
3. Put your MP3 file to project directory as 'voice.mp3'
4. in terminal run: python3 source-to-medium.py (here will be created 'medium.mp4')
5. enter your text areas contents if needed ...it takes some time to convert source*.mp4 files to one medium.mp4
6. in terminal run: python3 medium-to-fin.py ...it will caltulate final video length dividing voice.mp3.length() / medium.mp4.length() = silent_fin.mp4.length() ...also it will add voice.mp3 to silent_fin.mp4 as audio track
7. Finally you've got youtube_ready.mp4 files

Warning: russian comments in sources!