I have read a fair bit on CBR, ABR, CRF and so on, but that applies to new rips.
I have some existing rips in MPEG2 that are in CBR of pretty good 17Mbps. I want to convert them to H264.
Would there be any reason not to choose the same 17Mbps CBR again for the conversion?
Could I get any improvements anywhere in choosing VBR or CRF?
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Just me, maybe, but I always use CBR. VBR may give you a bit smaller file size, but I seem to have less problematic playback with CBR and I have enough storage room.
What H.264 conversion program are you using? I mostly use VidCoder, H.264/AC3 at 18.5 CQ.
And welcome to our forums.
You can only decrease the qualitiy by re-encoding the existing MPEG2 files with h.264. If you go back the original sources you can get better quality at the same bitrate, the same quality at a much lower bitrate, or somewhere in between. If you recompress at the same bitrate the files will be the same size (aside from minor container overhead differences). Typically, h.264 can achieve the same quality as MPEG2 at around 1/4 the bitrate.
I would recommend using CRF mode. For example, I know that CRF 18 at x264's Slow preset delivers pretty good quality with pretty much any video. Bitrate based encoding (ABR, 2-pass VBR, etc.) is really only useful when you need files of a particular size -- like when putting a lot of video on a CD/DVD. In cases like that you want to use the highest bitrate you can while still fitting on the disc.
Last edited by jagabo; 28th Nov 2018 at 21:12.
But since I am doing it anyway, I was wondering if there is any advantage to change the original mode, which was CBR.
You recommend CRF 18 - but what if the original video is not up to that quality? What will happen?
And on the other hand, if the original quality is better than CRF 18, I would prefer to keep it that way. I have plenty of disk space.
There is probably no answer to my questions, I will have to try.
To the previous poster - I use Xmedia Recode for conversions
If you have plenty of disk space I would simply use MakeMKV, doesn't re-encode or change quality, basically size in = size out merely wraps the original in a MKV container. I've done this for my entire DVD and Blu ray collection. I have Plex on one of my setups and doesn't balk at any of my files. Basically I use a Popcorn A-500 media player connected via Ethernet to my NAS. If you haven't used MakeMKV it only takes a few minutes to process a DVD.BeyonWiz T3 PVR ~ Popcorn A-500 ~ Samsung ES8000 65" LED TV ~ Windows 7 64bit ~ Yamaha RX-A1070 ~ QnapTS851-4G
Format : MPEG-PS File size : 21.0 GiB Duration : 2 h 18 min Overall bit rate mode : Constant Overall bit rate : 21.7 Mb/s Video ID : 224 (0xE0) Format : MPEG Video Format version : Version 2 Format profile : Main@High Format settings : BVOP Format settings, BVOP : Yes Format settings, Matrix : Default Format settings, GOP : M=2, N=15 Duration : 2 h 18 min Bit rate mode : Constant Bit rate : 20.8 Mb/s Maximum bit rate : 20.0 Mb/s Width : 1 920 pixels Height : 1 080 pixels Display aspect ratio : 16:9 Frame rate : 24.000 FPS Color space : YUV Chroma subsampling : 4:2:0 Bit depth : 8 bits Scan type : Progressive Compression mode : Lossy Bits/(Pixel*Frame) : 0.419 Time code of first frame : 00:00:00:00 Time code source : Group of pictures header GOP, Open/Closed : Open GOP, Open/Closed of first frame : Closed Stream size : 20.1 GiB (96%) Audio ID : 189 (0xBD)-128 (0x80) Format : AC-3 Format/Info : Audio Coding 3 Commercial name : Dolby Digital Muxing mode : DVD-Video Duration : 2 h 18 min Bit rate mode : Constant Bit rate : 448 kb/s Channel(s) : 6 channels Channel layout : L R C LFE Ls Rs Sampling rate : 48.0 kHz Frame rate : 31.250 FPS (1536 SPF) Bit depth : 16 bits Compression mode : Lossy Stream size : 444 MiB (2%) Service kind : Complete MainBeyonWiz T3 PVR ~ Popcorn A-500 ~ Samsung ES8000 65" LED TV ~ Windows 7 64bit ~ Yamaha RX-A1070 ~ QnapTS851-4G
OK, so I have the two files -
"original" MPEG2 , CBR 17.2Mbps, size 12GB
converted to H264 at CRF 18 size 4.6GB
I was surprised that a pretty high quality setting will reduce the size so dramatically.
The two files when played at normal speed look identical. But comparing them carefully side by side on VLC player, trying to find the same frame, the higher Mbps older MPEG2 codec seems to show some detail that I can't see on the H264 with much lower bitrate and size.
Think of the CRF value as choosing how much quality to discard. At CRF=0 it is lossless -- you will lose no quality at all. But like with all lossless codecs you get a very large file. At CRF=12 it's difficult to see a difference between the source and the new file, even looking at enlarged still frames.
This is basically what I would like to see somewhere - a table showing relationship between CRF and bit rate.
So if I have a rip, say, at CBR 20Mbps, and I need to re-encode, what CRF should I set to take advantage of the original high bit rate for the difficult frames, but save some storage space in the easy ones.
I said that I don't have shortage of storage, but with a large number of files it eventually could be a factor, and maybe it could speed up the conversion process that takes hours.
So, you'll find no such table or graph.
...what CRF should I set to take advantage of the original high bit rate for the difficult frames, but save some storage space in the easy ones.
I usually encode DVD rips around CRF 18, but Blu-ray rips around 20. The idea here is that the small defects will be made more visible when the small DVD frame is upscaled to full screen for viewing.