MP4 (h264+AC3) How to modify the volume without reencoding the h264 ?

[nimook]

Hello, i have many video clip created with HandBrake in the MP4 container. All these MP4 contain h264 for video, and AC3 for the audio.

The volume of all these clip is not the same, some are very low, others are high. I would like to increase/decrease the volume of these video.

After few days of research, i'm unable to find a shareware able to: change the volume of the AC3 without reencoding the h264 from my MP4 file.

I don't want to reencode the h264, because my video encoding has been done perfectly with HandBrake, and i don't want to modify/reencode that.

So i tried the following: demux my MP4 to have h264 and AC3 separetly. Modify the volume of the AC3, and remux my AC3 with h264 to obtain a new MP4.

Unfortunatly, for an unknown reason, every shareware i found to demux, are unable to demux correctly my videos. Even when i didn't change the volume of AC3. I try to just demux and remux without changing anything, and the result is the AC3 became not synchronise with the video. I tried all shareware i was able to find to do that, which include MP4demux and MyMP4BoxGUI and others, but all of them desynchronise the sound of my video a lot.

Because these shareware fail to demux and remux my video, i think the best way to do what i need, is to find a shareware able to increase/decrease the volume of MP4 video containing h264+AC3 without reencoding the h264, but i can't find any shareware. Please, help would be greatly appreciated to solve this problem.

[videobruger]

MediaCoder:

On the Video tab select Copy
On the Audio tab select codec (AC3)
On the container tab select MP4
On the Sound tab select Gain

Press Start

[poisondeathray]

Maybe you used VFR (variable frame rate) when encoding with handbrake ?

If you demux and remux without timecodes it will be out of sync

[nimook]

Thanks for the answers;

videobruger, I tried it on a video, and it worked better than everything i tried. I also had to choose Channels "Original" in the Sound tab to have a better sound. I will try it on others videos to be sure it work and it synchronise, but after the first try, it seem to work! If i increase the sound of 16db, the sound quality change slightly, but i guess it's normal. Thanks for the help

poisondeathray, I think i didn't used VFR with Handbrake. In the Video tab, i choose Framerate "Same as source" and for Quality i choose"Constant Quality". Thanks for the help

[poisondeathray]

I think older version of handbrake "Same as source" usually encodes VFR. (The base FPS is the same, but repeats and duplicates would cause handbrake to encode VFR)

In newer versions of hanbake (or nightlies) there is a radio box under FPS that has either CFR or VFR choice explicitly

For the audio , you might consider normalizing instead of choosing some random gain value (you might clip the audio). Search for audio normalization filter, not sure if mediacoder has it (most software should) .

In the future, you should normalize the audio before converting or encoding it (in the first place)

[T_Jet]

poisondeathray, I think i didn't used VFR with Handbrake. In the Video tab, i choose Framerate "Same as source" and for Quality i choose"Constant Quality". Thanks for the help

Handbrake uses VFR by default and some programs can have problems with it. Constant has to be manually selected on the video tab. You can also create your own presets with it set.

[FubarTheInsane]

I am trying to boost the volume on my .mp4 video too and I've followed these instructions however when I click start to convert it gives me an 'Error (19)'. When I play the video that's created, the volume completely cuts off halfway through. Any help offered would be much appreciated!
*EDIT

Sorry I'm using MediaCoder (0.8.26.5566). Container is MPEG-4. Video codec is AVC1. See screenshot for more info. Is there any other info which would help?

[Attachment 20466 - Click to enlarge]