Replace/Swap Audio in mp4 Video with Quicktime Pro

[Blaise Douros]

Why on earth would you go through this ridiculous process when you obviously have access to the Adobe suite (since you did the animation in AE? Just bring your lossless video file into Premiere, as well as your new audio, sync them up in a timeline, and re-export. Heck, bring them into AE, even! You’ll have more control using literally ANY method other than the one you propose, and you won’t be stepping on your quality by recompressing the mp4 file (which is what will happen if you do it this way).

There’s no point in using a stupid workaround with questionable amounts of control and quality when the regular way will work just as well and give you better results.

[Mika1976]

is there a way to replace just the audio in a mp4 video with premiere or after effect without rendering?
that’s the beauty of the quicktime pro process, or am I wrong? I don’t have to render/just any new codec/compression!!

I can clearly import the lossless .mov file into after effects, turn off the audio, add the new one…
but then I have to render again through the media encoder for losless mov and then compress it again with sorenson to youtube compatible mp4 file…

can someone else confirm that I don’t loose quality with this process?

I’m loading the two mp4 (old and new with replaced audio) inot after effects and I’m looking for artifacts…

Thanks for sharing your experience!
Mika

[Andrew Somers]

Hello Horst,

A couple things:

1) The majority of quality is lost on the FIRST iteration of a DCT type of compression. After that, even if it is re-compressed, the quality loss is minimal (assuming the same data rate.)

2) Sorenson is a dead and discontinued product. Adobe Media Encoder (AME) is just as good and integrated into the Adobe workflow. AME and Sorenson BOTH use the MainConcept codecs for mp4s if I am not mistaken, but I think you’ll find AME is better/easier/faster. If you have a reasonably fast computer with multiple cores, expect AME to fly through the render at close to real-time speeds (if not faster), depending on the frame size, frame rate, etc.

3) How long is this video? You’re making it sound like it’s a huge hours long piece! If you have the lossless file, I’d suggest re-syncing the new audio in AE or Premiere, and outputting using AME.

4) If you do the quicktime trick, it is CRITICAL that you SAVE AS and make certain to select “make movie self contained”. If you don’t, the QT will not play unless the source files are with it.

5) I’d be more inclined to swap the audio on the lossless version, then compress that in AME.

Related comments, but not what you’re asking about:

A) The “lossless” codec is a joke, and it’s not worth using. It’s 8bit, and you’ll get better fidelity using a 10 bit ProRes codec as your “master” render output. Other things being equal, bit depth is moe important that compressed vs uncompressed. And the prores file will be smaller, so it will be easier to handle and will render faster due to the lower dats bandwidth.

The “lossless” codec is a data hog, and you don’t get any real benefit for that data space it eats up.

B) I rarely use the audio features in After Effects. It is so much better to work with audio in FCP, Premiere, or Avid. My suggestion is to put the lossless video into Premiere, sync the new audio there, and then send it from Premiere to Adobe Media Encoder for output to mp4.

C) Since it sounds ike quality is important to you, in AME, make sure you set “two pass encoding” and set as high of a profile as you can, relative to the final file size you need.

Best of luck!

Andy

Andrew Somers
VFX & Title Supervisor
https://GeneralTitles.com

[Mika1976]

Thanks for your awesome post and advice!

It’s a six minute audio animation and you are right, I will try to replace it in after effects and render it out into “lossless” with the adobe media encoder…
about sorenson: I did some testing, and call me crazy: the result was always better!! maybe my media encoder setting were wrong…

but!
I did these quicktime replace steps and I really like the results:
– I compared the video mp4 in after effects and there was no artifacts or whatsoever…
– the replaced audio was AAC 320kb 48Hz 16bit: same here…

I think that is a quick work around with no negative outcome 🙂

[Blaise Douros]

Do what you want, there’s no video police. But personally, I’d rather have the additional control of a new export (which only takes a minute or two), rather than a questionable copy-paste operation.

[Steve Bentley]

You can also use FFMpeg to strip out the old audio and add new audio without reencoding the video portion.