1080p to 720p video file size larger than expected

[taso1000]

I have been trying out your BD Rebuilder program v0.38.03 and I like it very much. What I am trying to do is convert my blu-ray collection to 720p and save on my fileserver. I don't plan on upgrading my 50" 720p tv any time soon due to viewing distance and I'd have to go to much larger screen size to see 1080p resolution. While I see the 1080p to 720p option available I have a problem with the sizing settings. When I try the different encoder quality settings the video file size ends up larger than expected and not much smaller than 1080p. I don't want a file size upper limit/restriction like dvd5, dvd9 or bd25. It seems the 720p video file should only be 44% of the 1080p video file and theoretically bitrate should follow the same ratio per my understanding. I just want to resize 1080p to 720p video without compression plus high definition soundtrack. Are there custom configuration settings for what I'm trying to accomplish? I've tried auto, high speed through highest encoder quality settings but I'm not getting the expected video size reduction. Thank you in advance to who ever can help me or point me to a guide/instructions because my searches have been fruitless.

I'm still on the fence about movie only or full copy.

[Video Dude]

Select 'Custom Target Size' and change the value to your desired output size.


I just want to resize 1080p to 720p video without compression plus high definition soundtrack.
You have to compress to resize 1080p to 720p.
If you keep a high definition soundtrack that is PCM, you might need the BD25 size to retain video quality.

[jwjohnson]

If you are concerned about space I would ditch the LPCM soundtrack. Most people can't tell the difference (arguably no person can on consumer equipment - but I don't want to go there.) Also, since you have to re-encode anyway why not compress it a bit. With the right settings I doubt you can tell which is which. Again, if you are worried about space go for the movie only backup. It's nice not having to skip over a bunch of trailers and just start watching the movie. If you want the absolute best of everything - put more/bigger drives in your media server.

[jdobbs]

Seems a little strange to sacrifice video -- the main component and something that is readily apparent when watching, but then insist on keeping HD audio, which is undetectable to the human ear.

FYI: BD-RB will not allow HD audio unless your target is greater than BD-9.

Curiouser and curiouser.

[taso1000]

First of all, thank you all for your suggestions.

Video Dude, I don't have a desired ouput size constraint. I just want 720p and whatever file size it wants to be. I just thought it would be half the 1080p video size.

jwjohnson, I'm one of those that "has" to have the "True HD" and "DTS-HD Master Audio" show up on my receiver so that I know what I'm getting. ;) I can hear the difference between DD and True HD, whether True HD gives more ambiance is debatable. I'm most likely going to do movie only. If I want extras I'll grab the disc off the shelf. If I upgrade to 1080p I'll just re rip everything. And yes, I need more bigger hard drives. Doesn't everyone? ;)

jdobbs, I love your program, my reference pq and sound demo blu-rays will be original unmolested iso's. The rest will be converted to 720p. Everything goes through a Denon AVR-5308ci. I am of the opinion that the surround sound component draws the viewer into the movie atmosphere more than the video. Until I get a larger than 100" 1080p screen that is lol. We've been watching, what is it, 480i tv forever and still enjoyed the movie. But this is off topic and a whole different discussion. :)

I did find the BDREBUILDER.INI file searching the web and see an "ENCODE_QUALITY=" option but I don't know what the available settings are or what they do.

I hope this better explains what I'm trying to accomplish and thank you all for helping me.

[jdobbs]

"ENCODE_QUALIITY=" is set by the menu options. It isn't meant to be adjusted via editor (like hidden options).

[taso1000]

JDOBBS, would the FIXED_CRF option do what I'm trying to accomplish? I see the range is 10-50 with 10 being the highest quality. How does 10-50 translate to bitrate approximately and what would you recomend for 1080p to 720p conversion?

[jdobbs]

JDOBBS, would the FIXED_CRF option do what I'm trying to accomplish? I see the range is 10-50 with 10 being the highest quality. How does 10-50 translate to bitrate approximately and what would you recomend for 1080p to 720p conversion? There's no 1:1 relationship between CRF and bitrate. CRF will use whatever bitrate is needed (at that point) to keep the quality consist (based on the CRF). So a difficult section of video will use a higher bitrate, while an easy section will use a lower one. In the end the average bitrate turns out to be... well, the average of what it needed to keep that consistent quality level.

Size control is pretty much out-the-window with CRF encoding.

You get output that is nearly identical to the original with a CRF of around 18. As you increase the value you generally get smaller output with slowly lowering quality levels.