Audio Source and overall compression tradeoffs

[DavidG]

Ok I did read some threads but i have to admit i am a video/audio noob. That said.

I want to make a BluRay back up my Pirates of the Carribean 2 BluRay. The copy will play on a current BluRay player for my HD TV.

I first copied full disk to my hard drive. Now i was going to use that folder as source to copy just the "main movie" to a BD25.

With the movie, PCM/5.1, and no subpictures it is 28.6GB, so to fit on my 25MB disk it would need to compress to 78%. However if I chang the audio to AC-3/5.1 it is now only 21.6GB and no reduction.

So what is the audio / video trade offs between the two?

BTW, how do i know what the source audio format is? I have looked in the folders but it is not obvious to me (noob). As i heard that if the audio is not PCM to start with there is no advantage to upconverting to that format.

[DavidG]

Let me know if my post wasn't clear.

a) how do you know what the source audio files are from a BR Disk? Even when I ripped them "full disk at BD50" to the harddrive it seems like they are audio/video files.

Second what produces the better picture and sound quality
Using PCM that forces compression or just using AC3/5.1.

Thanks

[terry5]

The pcm audio tracks are much larger than ac3. You can get the audio info in the audio list in main form.

[hanibal]

You aint gonna notice much differance if any with that smal of compression. I do it all the time to keep the hd audio and still looks awsome.

[DavidG]

Hanibal, so you are saying stay with PCM and do the compression. I run this on a 65in HDTV so visual accuracy is important. Also terminology check. HD audio is not 5.1 correct?

[SuperFist]

AC3/5.1 is not HD audio but HD audio usually comes in 5.1 channels, just to clarify.

[hanibal]

i always pick the hd audio and i also have a 60 inch. Msome movies are compressed to 70-80 and can not tell the diff. And if u get a media player u can put the movie on as iso and loose not compression at all and keep any audio u want.

[DavidG]

Thanks hanibal.

Just a check on best practice. I hear it best to copy 'full disk' at BD50 to the hard drive and then source that file to burn a movie only BD25 BD? is that correct? What is the value of "clone" and should i use that over full disk to the hard drive?

thanks for the wisdom...

[Garry E]

Clone only allows you to do exact copy to BD disc > no output to hard drive. Copy 'full disc' to hard drive saves wear and tear on BD drive also better performance when processing from hard drive rather than optical drive.

[DavidG]

I must be missing something

On a burned BR disk, that burned at 1080p/H.264 and showing an 16:9 aspect ratio(No disk compression needed). Shouldn't that when played on a HDTV (with 1080p, 1080i capability)with 16:9 aspect ratio fill up the whole screen? In this case I have the black header and footer bars. Why?

I guess I must be missing something as 1080p and 16:9 on both would make it kinda obvious it should fill up the whole screen.

[SuperFist]

On a burned BR disk, that burned at 1080p/H.264 and showing an 16:9 aspect ratio(No disk compression needed). Shouldn't that when played on a HDTV (with 1080p, 1080i capability)with 16:9 aspect ratio fill up the whole screen? In this case I have the black header and footer bars. Why?

I guess I must be missing something as 1080p and 16:9 on both would make it kinda obvious it should fill up the whole screen.

That depends on the original aspect ratio of the movie. If I remember correctly, there is a difference between 1.77/1, 1.78/1 & 1.85/1 with the latter being the one showing black bars at the top and bottom. Hell Boy II: The Golden Army comes to mind.

[jayt]

Ok I did read some threads but i have to admit i am a video/audio noob. That said.

I want to make a BluRay back up my Pirates of the Carribean 2 BluRay. The copy will play on a current BluRay player for my HD TV.

I first copied full disk to my hard drive. Now i was going to use that folder as source to copy just the "main movie" to a BD25.

With the movie, PCM/5.1, and no subpictures it is 28.6GB, so to fit on my 25MB disk it would need to compress to 78%. However if I chang the audio to AC-3/5.1 it is now only 21.6GB and no reduction.

So what is the audio / video trade offs between the two?

BTW, how do i know what the source audio format is? I have looked in the folders but it is not obvious to me (noob). As i heard that if the audio is not PCM to start with there is no advantage to upconverting to that format.

David,
If you are truly wanting to back up your original Blu-ray movies, I wouldn't compress them at all. A blank BD-R goes for about 70 cents. If you have to, just spilt the movie in half and burn 2 discs. I never understood why people back up their original movies and compress them. If your dog eats your original copy of POTC and you have an inferior back up that is compressed what's the point. About audio, POTC has an uncompressed PCM track and then the standard Dolby Digital tracks which are in 5.1 surround sound. The PCM track is about 6,000 Kbps(kilobits per second) standard Dolby Digital or AC3 is only 640 Kbps, so you do the math and tell me which one will sound better. DTS-HD Master Audio and Dolby TrueHD are also uncompressed audio at different bit rates but all are superior to standard Dolby Digital.

As for video, 1920 x 1080 is HD video. 1080p just means how many lines of resolution are displayed progressively, sort of. Anyway Blu-ray discs are all 1080p or HD video, standard DVD is only 480i, so again which do you think looks better. As far as aspect ratio, if a movie is filmed in 1.78:1 AR it means it will fit on you 16x9 TV perfectly without any black bars. 1.85:1 will have tiny black bars on top and botton. 2.35:1 will have larger bars on the top and bottom. All these aspect ratios are still 1920 x 1080 lines of resolution, but some of the information is lost in the black bars.

If you are watching these movies on a 32 inch TV and have small satellite speakers then you probably won't notice if you compress them slightly and only have standard AC3 audio. If you are watching these movies in a dedicated Home Theater with a 100 inch screen and great sounding speakers then yes you will see and hear a difference. This is why compressing anything is not an option for me.

Blu-ray discs are the reason why watching movies at home is so great now because their is no information lost to compression anymore. Hope this helps.