longplay record (reduce mpeg in compressed domain)

[jamjam]

would it be possible to reduce the size of the mpeg-stream in realtime for recording in a bit less quality (for 1/2 ... or even 1/3 the size)

 

keywords: requantization, compressed domain transcoding

 

 

do you know of any dvb-recording software that does something like that in realtime?

 

if not, does a (freeware?) tool exist that does this reduction to (dvb-).mpeg files (not dvds)?

 

 

(i suppose technically a reduction of the resolution (1/2 horiz+vert) is not so easy)

 

******

 

for further reduction of also the sound-bitrate, one possibility would be reencoding the stereo-sound with lame at 96kbit/sec or less (haven't checked how much cpu-power this costs, but the quality would be ok for most purposes)

[Hartwig]

Why do you want that?? 1 GB harddiskspace costs only below 0,45 €

[Guest Oliver]

Oh, that's easy. Just buy a stand-alone DVB receiver and capture with an analogue TV-card. This way you can choose resolution, bitrate, color depth, etc....

 

Bye, Oliver

[jamjam]

Why do you want that?? 1 GB harddiskspace costs only below 0,45 €

<{POST_SNAPBACK}>

below 0,45? not quite, i think. (0,54?)

however, even big harddisks get full - and if I had half the filesize, I could record double the time.

 

Oh, that's easy. Just buy a stand-alone DVB receiver and capture with an analogue TV-card. This way you can choose resolution, bitrate, color depth, etc....

<{POST_SNAPBACK}>

 

That's much to difficult. The goal is only to reduce the filesize (with avoiding TOO big reductions in quality) and without _too much cpu usage_! If I can stay with the mpeg2-codec, good, but not necessary.

 

****

 

Can (and if, how - settings?) i recode in xvid,divx (..., other codec?) in (more than) realtime, with an acceptable result in quality and about half the filesize of the original mpeg?? (has somebody tried this??)

[yaRincewind]

Perhaps you can try this:

 

Enable the network streaming. Then take the VLC (VideoLanClient from www.videolan.org). Take the Network stream from DVBViewer as Input for the VLC.

Now VLC can convert and transcode the stream in realtime. Despite of streaming it to your network, you can also save it to disc I think.

 

I haven´t tried it by myself for now, cause I have some problems with the streaming server from DVBViewer. So I think I have to read a bit more documentation

[jamjam]

I have found something that goes into this direction, seems to become a

commerical product however (beta version).

 

They have implemented it as a directshow-filter. Something like this would be good,

perhaps together with a "plugin" (?) which lets you set/change encoding parameters

during recording (full ... 30%):

 

 

Hydrogenaudio Forums -> fast and high quality MPEG-2 Transcoding

http://www.hydrogenaudio.org/forums/index....showtopic=32222

 

Solveig Multimedia. Products - MPEG-2 Requantizer Component

http://www.solveigmm.com/?Products&p=MPEG2Requant

 

 

It is more for high bitrate mpegs (>5 Mps, ???)

 

I tried it with a 120 MB mpeg (without sound) ---> 73 mb -> 63 mb -> 59 mb

(i tried muliple passes, there are currently no parameters to reduce more than 50%

in one pass).

[jamjam]

I have found something else, this is GPL-code:

 

* M2VRequantizer:

A module which simply requantizes the video leaving the motion vectors unchanged. This module is very fast and provides relatively good quality.

* M2VDownsizer:

A module which recompresses the video stream completely (including motion vectors). This will usually yield slightly better quality, at the cost of time.

 

http://www.heise.de/newsticker/meldung/40594

http://www.dvdbrennen.com/modules.php?op=m...order=0&thold=0

 

http://www.metakine.com/products/dvdremaster/ (source download!!)

 

http://homepage.mac.com/major4/ (Mac-program ffmpegX that uses the code)

http://www.dealdatabase.com/forum/archive/index.php/t-30285 ("It does this by using M2VRequantizer from Metakine ...")

http://vdrportal.de/board/thread.php?threadid=5820

 

 

Perhaps a plugin with this code is possible??? (Someone wants to do this??? - should not be too difficult!)

 

*************** additional links:

http://www.linuxtv.org/mailinglists/vdr/20...3/msg01024.html (translation of heise article)

http://www.vdrportal.de/faq/index.php?sid=...1&id=32〈=de

("M2VRequantizer,überlange Aufnahmen auf DVD oder CD-Größe verkleinern")

 

 

http://www.google.de/search?num=100&hl=de&...tnG=Suche&meta=

http://www.google.de/search?num=100&hl=de&...tnG=Suche&meta=

http://www.google.de/search?num=100&hl=de&...tnG=Suche&meta=

Edited March 13, 2005 by jamjam

[darkman]

Solveig Multimedia. Products - MPEG-2 Requantizer Component

http://www.solveigmm.com/?Products&p=MPEG2Requant

 

It is more for high bitrate mpegs (>5 Mps, ???)

 

I tried it with a 120 MB mpeg (without sound) ---> 73 mb -> 63 mb -> 59 mb

(i tried muliple passes, there are currently no parameters to reduce more than 50%

in one pass).

 

Actually it operates properly with videos that bitrates less than 5 Mps.

But if you'll try to requant a video, say 4 to 2 Mbit per seconds, a quality degradation be distinguishable as block artifacts.

 

What bitrate has the video you have tested the requantizer with?

And what compression rates did you set?

[jamjam]

What bitrate has the video you have tested the requantizer with?

And what compression rates did you set?

It was (I think) already lower than 5 Mbps, as compression ratio i could only set 1/2 (in the demo version)

Edited March 16, 2005 by jamjam

[Technofriend]

Actually I think the makers of DVBViewer are not very much into this for the moment.

That's only what I think.

 

The question is, what do you want to do with it?

 

Realtime-recompression or only semirealtime-recompression?

 

Semi would be much more easy:

Write a script (I could do that too) to search the folder for new recordings and reencode them with whatever codec you want using an idletime-priority-standalone encoder.

After reencoding let the script delete the sourcefile.

 

Realtime-recompression:

would imho be best with a plugin from Requantizer-tools above. Should not be too difficult to do, but too difficult for me to do...

[jamjam]

Realtime-recompression:

would imho be best with a plugin from Requantizer-tools above. Should not be too difficult to do, but too difficult for me to do...

Now I tested the "requantiser" tool. Compiling under windows with cywin was no problem. Problem is however, the tool doesn't process .mpg files (with sound) directly, only .m2v, so demux is necessary (and remux after processing -- perhaps this is the real problem, because demux happens anyway).

 

The maximum compression I could achieve was 1/3rd (one step), even when setting a higher factor (5.0!). Time was 30-40 sec for a 120MB Mpeg (Athlon 1800), which is very fast (several times realtime).

 

Of course quality gets worse, so one should use smaller factors for films, etc. For recordings, where mainly the sound is important, you can choose higher factors.

I must say, that for many recordings in the past I had found this feature useful.

Edited March 23, 2005 by jamjam

[darkman]

What bitrate has the video you have tested the requantizer with?

And what compression rates did you set?

It was (I think) already lower than 5 Mbps, as compression ratio i could only set 1/2 (in the demo version)

<{POST_SNAPBACK}>

 

The demo version has no restriction.