exists an recompressor for h264 streams and audio streams?

[thometal]

Hi,

exists an lossless recompressor for an h264 + acc/mp3 stream included in an mp4/mkv container?

if not will it be possible to create one which recompressed it to 70% of orginalsize with ca. 10mb/s on of i7 with 4 cores? Or is this mostlikely not possible?


best regards

TT

[zody]

h264 and aac/mp3 are already lossy compressed formats. It is usually impossible to compress them further without loosing quality (creating a new stream with lower bitrate)

[schnaader]

I doubt something like this exists, because the closest thing would be Ocarina's (now Dell's) MPEG recompressor (http://encode.ru/threads/1111-Ocarin...deo-compressor) - this was two years ago and I haven't heard of something similar meanwhile, so it's pretty much state of the art.

Is it possible? I think so, but you should split "70% of size" and "10 mb/s" - 70% is possible for mp3 and MPEG-1/2, but h264 has better compression, so I'd expect worse ratios for it. Dell's MPEG recompressor states "15-25% compression at about 200 kbps", so speed is much worse than 10 mb/s, even if running at 4 cores simultaneously.

Note that creating such a recompressor is complicated, much work and lossy compression is much easier and common for video data, so doing this is more a proof of concept - you'll be able to lossy convert most video files to 50% of their size with existing tools and without much quality loss - and because of YouTube and similar streaming services, people tend to favor small size instead of high quality nowadays, at least for web videos, so most won't care about losslessness. On the other end of the spectrum, there are home cinema users that want very high quality, 6 or more channel sound and won't really care about the video being 4 or 8 GB in size. And, although it's getting more uncommon, there are still cases in which you'll have a fixed medium size (like 25 GB for a bluray disc) and need compatible, fast decompression with good quality instead of a filesize as low as possible.

Creating a new video/audio codec that gives 50% of h264/aac size with similar quality is another option. Recompression of existing videos is nice, but avoiding large new video files is closer to the problem's roots. CPU/GPU speed is evolving quicker than most of the bottlenecks (bandwidth, disk space), so codecs should evolve with it.

[Bulat Ziganshin]

if not will it be possible to create one which recompressed it to 70% of orginalsize with ca. 10mb/s on of i7 with 4 cores? Or is this mostlikely not possible?

if it would be possible, it would be a part of h264 itself

[thometal]

hm but the recompressed data stream dont need to be searchable etc. so maybe it can compress redundancies which is not possible for a video codec?

[m^2]

Bulat, h264 is a 2003 codec. Its successor is being prepared for quite some time already. Which doesn't change the fact that theometal's dreams are as beautiful as unrealistic.

[Sebastian]

if it would be possible, it would be a part of h264 itself

There are much better image compression systems than H.264, but they are computionally expensive which rule them out to be used in a video-codec.

[thometal]

Other question how much is the data stream compressed by calvc or cabac against if i would use neither? I know it would not be a compartible h264 stream. Exists any tools which can produce such a stream/file?

[Bulat Ziganshin]

even h264 itself can't handle 10mb/s on modern cpus, so slower codecs are out of question