How to convert an MKV file to MP4 that has two audio streams and I only need one of them with ffmpeg

audioffmpegvideovideo conversionvlc-media-player

The command I usually use in case of single audio stream mkv files to convert them to mp4 is:

ffmpeg -i location of mkv file\movie.mkv -c copy location of my usb stick\blablabla.mp4`

But when I did this command with an mkv file that had two audio sources, I ended up with no sound at all on TV and only English audio on PC, when I needed the Hungarian version. What is the command that converts mkv to mp4 while keeping only the audio source specified by me? If it's any help VLC says that audio track #2 is the Hungarian version.

Best Answer

Use the -map option to select specific streams.

First video stream, second audio stream:

ffmpeg -i input -map 0:v:0 -map 0:a:1 -c copy output

Or select all streams with Hungarian language metadata:

ffmpeg -i input -map 0:v:0 -map 0:a:m:language:hun -c copy output

I'm guessing your stream indexes in these examples, so you may have to adjust the actual values. Just probe the file first to see the details: ffmpeg -i input

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Convert specific video and audio track only with ffmpeg

You can use the -map option (full documentation) to select specific input streams and map them to your output.

The most simple map syntax you can use is -map i:s, where i is the input file ID and s is the stream ID, both starting with 0. In your case, that means we select track 0 and 4:

ffmpeg -i vidui.mkv -c:v libx264 -c:a ac3 -crf 20 -map 0:0 -map 0:4 vidui.mp4

If you want to choose video, audio or subtitle tracks specifically, you can also use stream specifiers:

ffmpeg -i vidui.mkv -c:v libx264 -c:a ac3 -crf 20 -map 0:v:0 -map 0:a:1 vidui.mp4

Here, 0:v:0 is the first video stream and 0:a:1 is the second audio stream.

FFmpeg Conversion – How to Convert MKV to MP4 with Subtitles and Change DTS to AAC or AC3

-acodec copy implies that you maintain the audio codec. Also, if your PS3 cannot keep up with the video codec, I would recommend converting everything.

The loss of quality in the conversion is usually negligible for video playback.

Try this:

ffmpeg -i in.mkv -c:v libx264 -c:a libvo_aacenc -b:v 35M -b:a 224k out.mp4

NOTE this values are quite high to start, so you could try lowering them if the file size is too much: 35M for 1080p, 15M for 720p, 5M for 480p

Best Answer

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Convert specific video and audio track only with ffmpeg

FFmpeg Conversion – How to Convert MKV to MP4 with Subtitles and Change DTS to AAC or AC3

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