The sound from a movie download comes out of two speakers, but what about 5.1?

May 4, 2009 3:29 AM

These days a lot of movie viewing takes place from digital files sitting on a computer and downloaded from BitTorrent. In this environment, is it worth having a 5.1 type surround sound audio decoder? Do most of the movie files on BitTorrent come encoded as multi-channel surround sound these days? And to output 5.1 digital surround from a computer what does one need? A special sound card? Some kind of surround sound decoder separate attached to the computer via its optical out?
posted by skylar to computers & internet (11 comments total)

I watch movies from DVD in 5.1 via my laptop - to answer the second part of your questions, you do need a 5.1 soundcard in your computer. These come in analogue (3 - 5 output ports) and digital (1 optical output) flavours, as do computer speaker systems . . .

I made the mistake of buying an analogue speaker set that wasn't initially compatible with the optical 5.1 output on the laptop, so I did have to bodge the connection with a digital - analogue decoder between the two.

Dedicated decoders are pretty pricey - I found these 5.1 headphones to be the cheapest option, they come with a little grey box which along with digital inputs (optical and coaxial) and outputs (for the headphones) also has 3 analogue output ports which can be used to send 5.1 onwards to the analogue speakers . . .

A faff, and easily avoided by buying a digital speaker system, but it works well and the 5.1 headphones are pretty cool for watching films late at night without disturbing those I live with . . .
posted by protorp at 4:01 AM on May 4, 2009

downloaded from BitTorrent. In this environment, is it worth having a 5.1 type surround sound audio decoder?

"Worth" is a subjective term. 5.1 surround systems can cost anywhere from tens of dollars to thousands. Buy within your budget.

Do most of the movie files on BitTorrent come encoded as multi-channel surround sound these days?

"Most" is a subjective term. You can download a 600mb copy of Dark Knight that will have rough 2-channel audio, or you can download the blue-ray copy with advanced sound. It's whatever you take the time to find...

And to output 5.1 digital surround from a computer what does one need? A special sound card?

It depends entirely on what hardware you already have. Many mid-level motherboards offer mutli-channel audio output. If yours doesn't, then an add-on card is one option.

Some kind of surround sound decoder separate attached to the computer via its optical out?

Generally PC-audio relies on mini-plug out-puts for home theater audio. You can connect these to a standard 1/8" RCA out by using a converter cable.
posted by wfrgms at 4:04 AM on May 4, 2009

2CD (1400 MB) movies generally have AC3 audio, which is 5.1 channel. 1 CD (700 MB) movies usually have MP3 audio, which is 2 channel. DVD Rips (4 GB) will have the original Dolby Digital 5.1 audio.
posted by smackfu at 6:10 AM on May 4, 2009

The easiest way to handle the output part is to use a digital optical connection from your computer to a compatible receiver. You should also make sure that the player software is not doing 2-channel downmixing, but rather sending the full signal over to your receiver for decoding. VLC supports this just fine, but you need to choose the pass-through option and set it as the default (if desired).

This is what I've done with a Mac used for a home theater and it works great for not only downloaded shows with the appropriate sound track, but physical discs as well.
posted by odinsdream at 8:28 AM on May 4, 2009

Surround is overhyped. Do you really need to hear that lazor coming from behind your head? Do you really need to wire up 5 speakers in your tv room and sit in the one exact spot that makes it work?

Some people do. Most people don't.

To answer a part of your question, no, most movie torrents do not come with surround sound, or even good sound. If that's where most of your movies come from, a 5.1 system would probably be a big waste of money.

If you have a bitchin' home theatre and rent or purchase hi-def movies with 5.1 soundtracks and love it when lazors zap behind you, then you know what to do.

Otherwise, not so much. Just crank up the stereo (you DO have a subwoofer, right?) and enjoy.
posted by Aquaman at 8:50 AM on May 4, 2009

Smackfu's heuristic matches my own experience.

A movie you only watch once really only needs stereo. Then, if you love it and want to watch it 100 times... download the huge 4Gb one or go buy a disc already.

(I think studios should just release low-res, mono-only versions of ALL their movies for free on iTunes or BitTorrent. People would watch many more movies and probably end up paying for more of the good ones. I guess it would end the cash cow of bad-movies rented once, though.)
posted by rokusan at 9:39 AM on May 4, 2009

Be careful! Just because you have a digital or optical out does not mean your soundcard is capable of processing full surround sound. Confusingly my old Asus motherboard did this fine but my new P5QE kept downmixing to 2 channel. This is a hardware problem and not a software problem, there's no way to passthrough the 5 channel surround. Very frusterating. My mac through a mini SPDIF converter plays surround sound just fine. It has something to do with the nvidia chipset and royalties or something. I got way into how 5 channel sound was passed through. To its credit there was an analog option for 5.1, but my receiver did not have analog inputs.

The simplest way to detect whether your video file has the capability to output surround is to open it in VLC and look under audio, if the surround sound option is available you are good to go. In my experience nearly all movies I've acquired have full surround, unless they are some sort of screener.

BTW I highly recommend downloading or ripping reference movies. For example I have Cloverfield in 720p, 1080p and surround sound. I know for a fact the settings are correct, so if I move to a new system I can quickly determine why something is not working correctly.
posted by geoff. at 11:02 AM on May 4, 2009

A cheap way to get surround sound without having an external receiver and speakers is just to hook up another set of computer speakers (or two) to the additional mini jacks for Center, L/R surround. Most computer speaker sets don't have optical inputs.
posted by wongcorgi at 11:05 AM on May 4, 2009

Surround is overhyped. Do you really need to hear that lazor coming from behind your head? Do you really need to wire up 5 speakers in your tv room and sit in the one exact spot that makes it work?

Agreed 100% - I bought into the whole hype early on. That system is now in the basement and rarely used. The biggest problem I found with multi-channel sound is that you would invariably have to muck with the center (spoken audio track) volume to actually hear the dialogue. Sure, the effen explosions would knock your socks off and the lazors would be behind you, but you couldn't hear what anyone was saying....
posted by jkaczor at 7:15 PM on May 5, 2009

This is what I've done with a Mac used for a home theater and it works great for not only downloaded shows with the appropriate sound track, but physical discs as well.

Odinsdream, to save 30 more followup AskMes, would you mind briefly listing the hardware/software components you settled upon?
posted by rokusan at 8:56 AM on May 6, 2009

rokusan:

I have a Mac Pro hooked to an Onkyo 504-series receiver with an optical digital cable. In System Preferences I've set the default audio output to digital.

In VLC I've selected "Built-In Digital (Encoded Output)" as the audio output device. This means VLC will not try to do anything special to the audio track before sending it to the receiver. As long as the receiver you have is capable of understanding surround sound formats this will work fine.

Before I got a center-channel speaker it was a little difficult (as mentioned above) to hear the dialog track over the sound effects. Once I added a center-channel speaker this problem was completely resolved.
posted by odinsdream at 9:46 AM on May 7, 2009