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General question about audio bitrates

Posted: Wed Oct 17, 2018 12:08 am
by curtisday
Is there anyway to set Ac-3 5.1 audio to 192 bitrate?

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 1:12 am
by Woodstock
Depends on what your source is. If it's less than 192, it is worthless to throw bits at it. If it's already AC3, your best bet is to pass it through, rather than doing anything to it.

But, have you tried using the pull-down for the bit rate?

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 1:32 am
by curtisday
I thought the pull down was the only way to set the bitrate. I'm converting a lossless MKV so the Audio is starting as DTS-HD MA and I'm trying to make it AC3 5.1 48 and 192 but the lowest bitrate in the pull down is 224. Basically I'm trying to replicate the iTunes Store quality (regardless of how pointless this seems).

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 3:11 am
by Woodstock
192 is possible if you're doing 2-channel stereo; 224 is the minimum total bandwidth for 5.1 down mix of a 5.1 source.

The increase in file size is not really that much, though.

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 12:40 pm
by Rodeo
IIRC AC-3 5.1 is encoded at 384 or 448 Kbps on the iTunes Store (just like on DVDs). With a codec like AC-3, encoding 5.1 at 192 Kbps will give you pretty bad audio quality in most cases.

The bitrate ranges offered by HandBrake for AC-3 match those of the official Dolby encoder (or at least did when it was checked).

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 3:26 pm
by curtisday
When I view the media info on iTunes Purchased movies it lists the AC-3 5.1 as 192kbps. I checked on several titles.

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 3:54 pm
by Rodeo
It could be "Dolby Surround" (2 channels).

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 4:42 pm
by curtisday
There's 2. the dolby stereo audio is 160 and the AC3 5.1 is 192

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 4:43 pm
by Rodeo
Can you post a screenshot of the MediaInfo report?

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 5:34 pm
by curtisday
https://ibb.co/hyROi0

That's from a purchased iTunes movie. It's the 5.1 stream.

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 5:47 pm
by curtisday
My apologies! after using a different app it says it's 384! so sorry for the mixup!

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 6:33 pm
by Rodeo
Not sure which interface to MediaInfo this is, but it's pretty useless… it doesn't show the channel count. But that 192 Kbps stream must be 2-channel.

Re: General question about audio bitrates

Posted: Wed Oct 17, 2018 6:38 pm
by curtisday
It was from VLC. It just gave the wrong info, when i used MediaInfo it said that stream was 384. Sorry for the misunderstanding! My bad!