Compressing Audio

[Bacender]

Howdy everyone,

Just wondering if there's a way to take a look at the overall audio data size in a video?

I just compressed a video using H264 at 25 quality, yet the 5 minute video at 1280x720 was over 350MB.

So i'm wondering,

- Is there a way to take a look at the size of the video and audio data separately?
- What is the best full audio compression codec to use for vDub? Please offer links, and possibly a guide/suggestion to the quality setting i should use.

Thanks

[jman98]

You don't have to do this, but people who use H.264 for video often use AAC for audio. You're not going to find massive space savings by moving to AAC over some other format though, but it might help a little. Worrying about compressing audio to save precious space is kind of like agreeing to spend over $1000 US for a television and then worrying about finding a place that will sell you the TV for 1 or 2 dollars less. Audio doesn't take up that much space compared to video that worrying about it is really worrying about the wrong thing. If the file is too big then you need to encode the video with a lower bit rate. Re-encoding audio down is just a waste of time in my opinion. You won't save much space unless you do some things that will make the audio sound really bad. Sounds to me like your problem is with however you encoded the video. I don't encode to H.264 as my PC is too slow for that so I can't help you there. Maybe your quality setting is too high and it used a very high bit rate. I very roughly estimate a video bit rate of 9000 Kbps for your video file which under some circumstances might be considered too high (or might not - it depends).

[PuzZLeR]

Worrying about compressing audio to save precious space is kind of like agreeing to spend over $1000 US for a television and then worrying about finding a place that will sell you the TV for 1 or 2 dollars less.

That and the fact that for those "savings" you will instead get a TV that has its audio output channels damaged and emitting a weaker quality of sound...

[manono]

Just wondering if there's a way to take a look at the overall audio data size in a video?

GSpot should be able to break down the video and audio sizes.

[PuzZLeR]

I just compressed a video using H264 at 25 quality, yet the 5 minute video at 1280x720 was over 350MB.

It all depends on the complexity of your video - 350MB may be a good size for 5 minutes of high quality high action/motion video at that rez. But it would be very high, for example, of a video of someone just standing and making a speech. When you mean 25, do you mean CRF=25 for x264? That should have generated a smaller file size than 350MB for most sources (and of course weaker quality). The lower this CRF number, the higher the file size and quality. (Many use between CRF = 18 to CRF = 22.)

Is there a way to take a look at the size of the video and audio data separately?

Not that I know of without an extra step. You can either demux the video and audio streams separately and determine the file sizes, or use a tool like MediaInfo which would tell you the bitrate for each video and audio stream, then you can enter that into a bitrate calculator for the file sizes of each.

What is the best full audio compression codec to use for vDub? Please offer links, and possibly a guide/suggestion to the quality setting i should use.

Like jman98 said, most people use AAC with H.264 video, but AC3 is gaining more and more popularity with it too. But most people never use VDub to create H.264 video as well. But there are many others. And I don't know much about audio encoding with VDub, which is really about video encoding. This is best left to a dedicated audio encoder. You can always mux the result (video and audio) in the end.

If the audio in the source is indeed AC3, it's best IMO to just keep it as such since you won't gain much compression going down to AAC, or even MP3, but you will notice the quality loss.