Compression: How much video quality loss?

[Djard]

I understand that the more compression, the more the video quality loss, and that you cannot improve the original video quality by increasing the bitrate. But is there actual video quality loss if you convert to another format, like converting an AVI file to an MP4, using the "lossless" H.264 or Huffyuv codec?

[guns1inger]

In theory, no. Lossless means lossless. There may be some drop due to colour space conversion depending on how you do your encoding, but otherwise, quality out should be the same as quality in.

What you will get are huge files. A 1.5 GB 2 hour SD H264 might turn into a 60GB Huffyuv file, for example.

[Djard]

Thanks. No problem with space because I don't save the source file after converting and burning to DVD media. The only reason I convert to AVI is because on occasion I want to cut out unwanted parts with VirtualDub, and I have not found any app that allows me to reliably clip .MP4 and .MKV files.

[ARTO65]

For cutting .mp4 and .mkv, you can try Avidemux, YAMB (mp4box gui), mkvmerge and solveigmm avi trimmer + mkv.
No guarantee any of those will work the way you want, but it's worth a try!

[Cornucopia]

Just so we're all clear - there is NO SUCH THING as "lossless h.264".

h.264 is a form of MPEG. As such, it uses both reduced Color Sampling, Intra-Frame compression and Inter-Frame compression. At it's best quality settings (which may not even be normally available), you might could set the color sampling to 4:2:2, the Intra Quantizing to the LEAST lossy as possible (for some reason, I can't remember if this is a LOW value or a HIGH value), and set the Inter-Frame to be ALL I-Frames.
But even then, you're still doing SOME colorspace reduction (it's not 4:4:4) and there is NO option for "No quantization loss" on an I-Frame. Even at rediculously high bitrates (higher than other "lossless" or uncompressed sources).

Visually, it may seem lossless to you, but it isn't.

Scott

[poisondeathray]

Just so we're all clear - there is NO SUCH THING as "lossless h.264".

h.264 is a form of MPEG. As such, it uses both reduced Color Sampling, Intra-Frame compression and Inter-Frame compression. At it's best quality settings (which may not even be normally available), you might could set the color sampling to 4:2:2, the Intra Quantizing to the LEAST lossy as possible (for some reason, I can't remember if this is a LOW value or a HIGH value), and set the Inter-Frame to be ALL I-Frames.
But even then, you're still doing SOME colorspace reduction (it's not 4:4:4) and there is NO option for "No quantization loss" on an I-Frame. Even at rediculously high bitrates (higher than other "lossless" or uncompressed sources).

Visually, it may seem lossless to you, but it isn't.

If the source is 4:2:0 subsampled, then yes ,there is a lossless h.264 format. x264 has this option. Decoded image is bit for bit identical, much like huffyuv or lagarith in 4:2:0 mode

h.264 as the larger standard supports unsubsampled 4:4:4, 10-bit, 12-bit , 14-bit Y'CbCr lossless encoding, but currently there are no available h.264 encoders for this type of lossless encoding, but the profile is in the official specs

[Cornucopia]

Granted, but I would never call 4:2:0 ANYTHING lossless. From a true 4:4:4 or 4:2:2 master, that's still a LOT of color loss.

I haven't seen this lossless spec, how do they get around the quantizing error?

Scott

[poisondeathray]

I haven't seen this lossless spec, how do they get around the quantizing error?

I don' t know the details of how it works, but it's in the JVT ISO documents under High 4:4:4 Predictive Lossless (H444P) encoding

But this is meaningless until a real implementation encoder & decoder is available

[Djard]

Thanks for the excellent info. I now recall losing some color in a project with a "lossless" encoder but thought it was caused by an error I had made in the settings. Thanks also for pointing me to AVIdemux, etc. I don't mind trying out new software since installing a wonderful registry edit tool that has a Explorer-like GUI and lets you quickly remove the thousands upon thousands of footprints left behind by so-called uninstallers. If anybody wants a copy of this gem of an app, it's available with a clear guide from the "Downloads" page at mednetconnection.com. Cheers.

[Bonie81]

going with cornucopia, there is a significant loss of quality and artifact introduction if you use any compression codec in lossless mode.
Normally I prefer HuffYUV or lagarith, for precise jobs.