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is there really a difference between DTS and AC3

post #1 of 16
Thread Starter 
Guys I would like to know is there really a difference in AC3 and DTS? I have a Pioneer receiver so I normally go with DTS. I just always wondered is there really that big of a difference because I've played back media that has AC3 and it still sounded great.
post #2 of 16
While there are technical differences, the sound output is pretty much the same. But, it's rare to have a choice on playback these days. Some DVDs offered both codecs. But, that's not the case with Blu-ray and it has never been the case with TV broadcasts or streaming services. You pretty much get Dolby or DTS, not both.
post #3 of 16
AS stated from a technical standpoint yes..

From a real world standpoint? That seems to depend on the equipment and the person listening to it.

ON MANY things I can honestly say I don't hear a difference between using Dolby and DTS, however there have been a few instances where I thought DTS just sounded better. I generally listen to DTS tracks whenever possible.

That also being said.. I watched Brave for the first time the other night and I honestly think that has one of the best movie soundtracks I have ever heard, it happens to be Dolby Digital so YMMV
post #4 of 16
I have several BRs that have both DTS-HD-MA and DD5.1 tracks. Oddly they usually default to the Dolby track until I change it. I don't think it's my imagination that the DTS track sounds better: clearer, sharper, cleaner for lack of a better term. Another thing I notice is that DTS generally plays louder so I don't need the same volume level as with Dolby. Perhaps DTS is always mixed differently?
post #5 of 16
Dolby and DTS have nothing - absolutely nothing - to do with how a soundtrack is mixed. Mixing happens when a movie is made and the soundtrack is mastered as multichannel PCM. It gets encoded for storage on a DVD or BD later on using one of the Dolby or DTS codecs, whose sole purpose is data compression to save space, much like zipping up a data file to make it smaller. So, again, there's no such thing as a Dolby or DTS mix.

If there's a visible DD 5.1 track on a BD, it likely uses the same low bitrate as the DVD version. It's not meaningful to compare a lossless dts-MA track to a low bitrate DD 5.1 version. I believe the OP is asking about differences between lossy DTS and DD 5.1.

As for volume, Dolby uses a bit of metadata called Dialog Normalization, which usually telles the decoder to lower the volume by 4dB. That's why Dolby generally sounds quieter than DTS.
post #6 of 16
Thanks for the explanations. smile.gif
post #7 of 16
DTS-HD-MA will usually sound much better than DD 5.1, or DTS 5.1 for that matter. It is lossless HD audio, whereas both DD 5.1 and DTS 5.1 are lossy compressed audio.
post #8 of 16
It depends on the bitrates. The maximum bitrate lossy outputs on Blu-ray rival lossless in quality. But, again, the OP is asking about differences between lossy DD 5.1 and DTS.
post #9 of 16
Thread Starter 
I agree DTS-HD-MA sounds great as it is uncompressed. I looked at AC3 and DTS since they are both compressed so I basically was comparing these two compressed sound formats. I can clearly see why uncompressed HD sound is in another league but it seems to me that compressed AC3 and DTS sounds nearly the same. Also does sounding a little louder really make DTS that much better? This almost comes down to how great of a surround sound system you are listening on.
post #10 of 16
Sounding louder doesn't make it better. Simply turn up the volume a little with Dolby sources and there's no difference in loudness.

btw, dts-MA is compressed, just like every other codec. (Codec means COmpression DECompression.) This is data compression, not dynamic range compression. The difference is that dts-MA and TrueHD are lossless, meaning all of the data removed in the compression step is restored during decompression. DTS and AC3 are lossy, meaning some of the data is not restored.
post #11 of 16
Quote:
Originally Posted by BIslander View Post

Sounding louder doesn't make it better. Simply turn up the volume a little with Dolby sources and there's no difference in loudness.

When I change the inputs on my receiver from optical to multi-chan in from my Oppo Blu Ray, the volume level decreases. Like stated, I just turn up the volume for much better audio.
post #12 of 16
Quote:
Originally Posted by Possumgirl View Post

I have several BRs that have both DTS-HD-MA and DD5.1 tracks. Oddly they usually default to the Dolby track until I change it. I don't think it's my imagination that the DTS track sounds better: clearer, sharper, cleaner for lack of a better term. Another thing I notice is that DTS generally plays louder so I don't need the same volume level as with Dolby. Perhaps DTS is always mixed differently?

DD5.1 has a lot of metadata that a properly licensed decoder has to respect. For example, the decoder will check the dialnorm value to first attenuate the volume to -31 dB correctly, whereafter it will apply any DRC (dynamic range compression) on the track as well. The result is that DD5.1 often is lower in volume, and more dull sounding, than a DTS track.

Usually one can simply disable DRC on the receiver, and raise the volume, to make it sound very close to the DTS track.
post #13 of 16
Quote:
Originally Posted by BIslander View Post

While there are technical differences, the sound output is pretty much the same. But, it's rare to have a choice on playback these days. Some DVDs offered both codecs. But, that's not the case with Blu-ray and it has never been the case with TV broadcasts or streaming services. You pretty much get Dolby or DTS, not both.

And ATSC mandates AC3 only. So OTA will be AC3 for a long time. While cable networks don't have this mandate, they will just go along to ensure compatibility with the receiver market.
post #14 of 16
There's also Dolby E. This is an in house broadcast format very similar to AC3 but with one important difference. In Dolby E the compressed packets are aligned with video frames. In AC3 they are not. Problem with AC3 is you can't edit it once it's joined with video. Dolby E was developed to meet this requirement.

Today AC3 is just a consumer distribution format.
post #15 of 16
If you look at best buys website they have some blu rays that say they are widescreen AC3. Does that mean they have a lossy soundtrack? I thought all blue rays had lossless sound.
post #16 of 16
A quick Web search of the BB site found AC3 is claimed for Blu-ray combo-packs. In other words, titles which include a Blu-ray and one or more DVDs in the same package. An example is World War Z.
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