Quick question on quality and file size...

[rxloren]

Hi all, new here, and it's real nice to find this very informative forum.. I have learned a lot just trolling around here. I thank you in advance for a little advise from the pros. I'm building a nice collection of movies (I already own) for my HTPC. I have a question on max file size and quality.
Let's say I wish to convert a typical 2 hour movie from a 15Gig MKV file to a more maneagable MP4. I use some great tools like AVIDEMUX which I found out about here, great software btw. I have played around with file sizes and I know the smaller the size the more quality will suffer. Playing around costs a LOT of time as sometimes my encode times are 8 hours plus!When I encode to mp4 i choose Mpeg 4, single pass using a bitrate calculator to measure bitrate. My target is about 1 gig/hour of film. and aac (faac) with a +6 gain on audio and I've had no problems. I will soon run out of space and in lew of getting a bigger harddrive (2 gigs on the way, lol) I'd like to conserve space.
My question is, given the source is real good quality, 1080p type mkv, and I copy the video and audio as above, what is the most I can shrink it down where quality will not be noticable on my 54" HDTV? 1Gig/hr, 500mb/hr? Taking in consideration of course real colorful movies like Avatar or "all time favorites" of mine I will use better settings, but for your run of the mill movie for family entertainment and bragging rights.. lol. where quality doesn't have to be the BEST, just great....
I have an HTPC with HDMI outputs that go stright into my TV, I use Windows Media Center and so far so good..
Eg: I took a 13Gig mkv of Gladiator and shrunk it to about 2.6Gigs and the quality is fantastic.... can I go lower?
Thanks again and I hope I'm not too confusing. LOL.
Regards,
Rx.

[guns1inger]

Use something like handbrake and do a quality based encode instead

[PuzZLeR]

Hi.

Obviously, in most cases, higher bitrate means better quality and slower speeds usually means better compression and quality per bitrate. But let me answer two questions most asked by new hobbyists that can spare them years of headaches.

Question 1: What should I encode to? What is the best format? What is the most compatible? Which has the best speed?

Answer: It doesn't matter. Use what's best for you now, whether it's DvD, H.264, DivX, Xvid, iPod, whatever, and whatever you can bear in terms of encoding speed and file size. As long as you keep a copy of your Source, you can always revisit your options as formats and preferences (always) change.

Good practice is keeping two versions of your video - Source and Target (four versions if you include backups). You should never go wrong this way.

Question 2: What is the right bitrate for this so-and-so that would give me the quality level in all my videos of so-and-so... ?

Answer: Every video is, and will always be, different and have different bitrate demands with lossy and compressed codecs. A scene with black screen will have lower demands than one of high motion like a fight scene. The best advice here is use quality based encoding - pick the quality you want and let it decide the bitrate for you in one pass. This alone made my life so much easier in this hobby using many formats, MPEG-2, DivX and H.264.

Hopefully 'Slinger and I changed your life.

[rxloren]

Thanks guys... I will try handbreak. Looks promising... As far as keeping the source, it's not practical for me atm. Most of the source files are 15Gigs plus in size... I'm doing MP4 for now, hopefully this format will stick around a few years...
Thanks again for your suggestions and answering the questions... you have indeed changed my like... lol..
I am open to more suggestions and comments... thanks again!!