Weird ffmpeg issue.... can anyone tell me why this happens?

[oofers72]

I am reauthoring a DVD of a music performance.

I used PgcDemux to get the elementary streams-- an m2v file and an ac3 file.

One of the reasons I am reauthoring is because the audio levels top out at about 0.11 of the max. It being a music performance, I want to boost those levels.

I do that to the ac3 file in Goldwave. Goldwave does not save in ac3, so I save as wav.

Then I use ffmpeg to convert the wav back to ac3.

The resultant ac3 file now has its audio levels maxing out at about twice what they were initally (now, it's at 0.22). But the wav file I created and used as the source for the ac3 conversion was absolutely, most definitely maxed out a 1.000....!?!

Why the drop in levels when I convert to ac3?

Furthermore, if I take the exact same wav and use ffmpeg to convert to mp2 instead, the maxed levels are retained.

It's really not a big deal, since I can remux an mp2 file in my reauthoring process just as easily as an ac3--- and since my mp2 is the one retaining the maxed levels, that is what I will do.

But out of curiousity, can someone tell me what is going on?

I suspect it has to do with the fact that ac3 can be a container for 5.1 sound? And for that matter, I do not understand why ac3 is used in cases when the sound is simple stereo.

Someone smarter than me shed some light, please.......

[Baldrick]

Try convert to ac3 with aften instead.

[aldaco12]

I never used aften, it might be a very good application.
In general, FMPEG GUI encodes in AC3 dropping the audio volume level. It instead encodes in MP2 with no peak loss.
Another possiility is using BeSweet plus its GUI callled BeLight.

[oofers72]

Thanks for the suggestions for alternatives....

...I realized that ffmpeg is for some reason cutting the level of the audio for ac3 conversion.

My question is why?..... I mean, what's the logic behind it doing that? And then not for mp2? A bug?

I hate ac3 anyway, and will just stick with my mp2 (files sizes are identical). But I will check out those other conversion programs for the future.

Thanks.

[celtic_druid]

From recollection it was a bug and it was fixed some time ago. Guess you are just using an old ffmpeg build?

[oofers72]

From recollection it was a bug and it was fixed some time ago. Guess you are just using an old ffmpeg build?

Yes I am. And that explains it.

Thanks!!