I've got an old interview with my grandmother that was saved as an mp4 file, but her voice is very low as compared to the interviewer. I'd appreciate if anyone can suggest a way to fix this. Would I need to extract the audio, increase the lower levels in Goldwave (or another program) and then re-multiplex the video and audio tracks? If so, are there any recommendations for a tool to use to de-multiplex and re-multiplex? Maybe there's a tool that will allow me to just work with the full mp4 file? Appreciate any advice!
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You can use Audacity with the FFmpeg addon.
Drag the video into Audacity and the audio will open. Fix the file (amplify the quiet parts) and export as PCM/wav
Open the video in Avidemux. At the top, Audio/select track/disable the existing audio.
and load the new audio
If you want to compress the audio, change the "audio output" on the left from "copy" to "AAC (FDK)"
Hit configure if you wish to increase the bitrate beyond the default 128
I just did this three weeks ago with some 1955 transcontinental telephone conversations.
Back in the 1950s we didn't have digital and didn't have satellites, so long distance phone calls were carried over regular telephone wires (and later microwave links) and re-amplified every few miles. As a result, the voice on the far end was very weak in many of these recordings. I used iZotope RX (Audacity is the closest free tool that does similar things). I selected each quiet section and amplified it (tedious work). However, I then took a noise print of small sections where no one was speaking in the sections I just amplified, and fed that noise profile into the noise reduction module in iZotope RX. I applied that NR to each section that had been amplified. This worked wonderfully to keep the noise profile of the amplified section sounding very much like the background noise of the un-amplified section. This avoided the jarring jump in the noise floor every time the conversation changed to the other person.
Last edited by johnmeyer; 19th Aug 2020 at 18:50. Reason: typo
Thx guys! I'll try that this weekend!