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sbekin01
sbekin01
Participant
October 20, 2014
Question

Replacing an audio track without re-encoding the video

  • October 20, 2014
  • 1 reply
  • 18921 views

I'm new to Audition CC so apologies for the basic question. I originally asked this in the Premiere Pro forum but I think it's more an Audition question..  I have AVCHD home video (MTS video with AC3 stereo audio) and have found I can clean up the audio, for example in speeches, very well in Audition. Is there a way to just replace the MTS's orginal audio track without re-encoding the video (which it seems I have to, if I do this via Premiere Pro)? In some cases the videos are poorly lit and any re-encoding makes them look noticeably worse than the original. In any event the video does not need re-encoding, I just need to replace the audio. Maybe I need to export the cleaned-up audio from Audition and use some other program to replace the audio in the original MTS file? Is that called re-muxing?  Thanks in advance for any help.

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    1 reply

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    emmrecs
    Legend
    October 20, 2014

    I don't have PP so can't be sure of this, but in the video editor I use the "audio" is always displayed as a separate "track" on the video editor screen.  If I want to replace the camera audio I simply place the replacement audio, exported from Audition, on the next available track, ensuring it is correctly lined-up with the existing audio track (to ensure lip-sync etc.) and then either mute or delete the original audio.  (Not sure about PP, but in my video editor I have first to "ungroup" the original audio from its video track to be able to delete it; once I am happy with the alignment of the "new" audio I will "group" this track with the video to ensure they stay locked together.)

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    Olly_
    Participating Frequently
    October 20, 2014

    I have done that, by opening the MTS home video in Premiere Pro CC, selecting the clip in the Timeline, selecting 'Edit', 'Edit in Audition', 'Clip', which opens the audio track in Audition CC, where I clean it up and save, which returns me to Premiere Pro and I can play the combined result... the original video and the cleaned up audio track, which has replaced the original audio track. However it's the next step that foils me... To get a new MTS file with the new audio I have to save the changes, which re-encodes the video, which gives me a larger finished file with noticeably worse quality! So I'm starting to see that Premiere Pro can't do this. It has to re-encode the video as well as combining the new audio and I can't see any way to do that without video quality loss.

      On a positive note I think there's a way that I'm still checking. I can drag the MTS straight into Audition, fix the audio, save the audio track as a new AC3 file (in my case checking it's 48khz, stereo, 16bit, 256kbps and Dolby Digital, not Dolby Digital Plus) and then use an open source program Avidemux to open the original MTS video, leave the main screen settings as Video Output..Copy, Audio Output..Copy, Output Format..MKV Muxer (not sure about this option, there may a better choice) and in the Audio menu..Select Track, in the Track 1 dropdown..Add Audio Track, then OK, play to check it's OK, and Save as a new MKV video file. The change in container from MTS to MKV seems OK and there's no video re-encoding. It's very quick, there's no video quality loss, the new audio is seamless and in-synch, the final file size is very similar to the original, and 'Media Info' shows the key internal video and audio specs are the same as in the original MTS video. I'll test some more and see if there are issues I haven't seen yet (I've only done one video so far).

    Bob Howes
    Bob Howes
    Inspiring
    October 20, 2014

    This is actually more of a Premiere Pro question than you know.

    MTS is just a wrapper extension for a variety of video types...and the AVCHD you mention is (as I understand it) based on MPEG 4 coding.  One of the things with MPEG coding is that audio doesn't exist as a discrete file as separate from video--both audio and video are coded together.

    However, after you've edited in Premiere Pro (even if it's just opening the video to process the audio) on export you have a wide selection of export formats.  Depending on what you want to do with the videos once you're done, you should be able to find an export format that does little or no damage to your original quality.  However, you'll need to think about what format/codec is most suitable for what you want to do with your finished product.

    ...and, on that I suggest you may wish to visit the PP forums!

    Edited to add...I forgot to mention that a little utility called Media info is very useful to analyse exactly what format your original files are:  MediaInfo

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