Audio volume compression

[fhutt]

I have problems with some movie videos. The speech can be hardly heard while actions scenes can be heard in the whole neighbourhood on the one volume setting.

The answer would be to compress the audio in the codec. I am not talking about file size compression but reducing the volume of the loud passages and leaving alone the volume of quiet passages.

Is there such a codec and could this be implemented in Avidemux?

[eumagga0x2a]

Is the audio track stereo or multichannel (5.1 or even 7.1)? You provide zero information about your platform and whether you experience the problem in all players or in Avidemux only (Avidemux downmixes multichannel audio by default and it doesn't have a choice on Windows due to a very old interface it is using), but in general such a problem is typical for watching videos with multichannel audio on a system with stereo-only equipment wihtout proper downmixing.

If the above doesn't apply to your case, the tool you want is called dynamic range compression (DRC) and there is a corresponding checkbox in Avidemux audio filters. Unsure whether it works though.

[fhutt]

Sorry for the delay in replying.
The problem is already in the source. So, it may be that the this source is or has been a multi channel audio. Avidmux was not the problem causing this.
I am just looking for a way to fix it or even just improve it.

Some of the videos I am transcoding are videos with a 1920x800 aspect and I convert them to 1920x1080 to fill the screen. I understand the I need to cut off the sides. This has worked fine so far. I just wanted to find out if there was something I could do about the "dynamic range compression (DRC)". I must admit I didn't realise the checkbox existed. Even if had noticed it I would not have known what it meant.

Thanks to your reply I have now tried it. I extracted the audio with VLC from the original. I also extracted the audio from the Avidmux result. I placed these videos into Goldwave that shows the waveform of these audio files. The Avidmiux result with DRC was not flattened completely, but, the dynamic range has certainly improved markedly. The very low volumes have increased and high volumes reduced. I think that it is worth using this feature of Avidmux.

I used the aac(lav) codec. I don't know the difference between the different aac codecs. So, which do you recommend for general use?
Thanks

[eumagga0x2a]

Some of the videos I am transcoding are videos with a 1920x800 aspect and I convert them to 1920x1080 to fill the screen.

I suspect this step should not exist. I'll try to come back to this topic later.

I used the aac(lav) codec. I don't know the difference between the different aac codecs. So, which do you recommend for general use?

From the 3 different encoders available for the same AAC codec, the one from libavcodec ("lav") is totally fine, but if you need features like SBR to improve quality at very low bitrates (HE-AAC mode), you need to use the FDK one, which is also totally fine. FAAC is very fast (which is irrelevant) but is deemed inferior in quality (which matters).

[fhutt]

Thank you for your explanation about the different aac codecs.

With regard to transcoding, my TV set running 1920x800 shows black bars on the top and bottom of the screen. By watching this I loose some screen real estate.
Cutting the sides out appropriately and transcoding to 1920x1080 fills the screen and the focus of the objects (centre of screen) is not lost.
My logic may not be acceptable to some because, yes, some of the picture is removed. To me, this is acceptable.

[eumagga0x2a]

You are right, for me personally the loss of information from cropping combined with quality loss from re-encoding would have been inacceptable, I should not extrapolate this view to everyone. Some TV sets allow to do overscan pretty generously, but maybe yours don't.