[MEncoder-users] Need some hints for my tv recording concept

[Gerhard Brauer]

Hi,

it's my first posting on the list and i would like to get some special
hints for an generally exercise: tv recording on pc.

First: at the moment, after researching and try-and-error, i have (for
me) a working concept for recording and watching on/from tv. But i'm
sure there are things i could do better.

My equipement ist low: i use a digital sat receiver. A friend gave me
his old analog tv card, which i connected over s-video with the
receiver. My vcr-pc is a 500Mhz P3, don't laugh ;-), with an ATI Rage128
tv-out. For me, it's a null cent solution to record and watch video/dvd.

My first tries goes to record at full pal resolution, but therefor my pc
is to slow (video buffer full) when i must use a compressed video codec
(mjpec i think is good codec for real time).  After accepting this i
used solution A:

A) record at 352x288
These are the parameters for my mencoder record script:
 -------------INPUT ---------------------#
 ##
 ### TV
 TV="driver=v4l2:device=/dev/video:input=1:amode=1"
 TVOPT=":mjpeg:decimation=2:quality=100"

 # ------------ OUTPUT --------------------#
 ##
 ### VIDEO
 VID="lavc"      # -ovc
 VIDOPT="-lavcopts
 vcodec=mjpeg:mbd=1:autoaspect:abitrate=128:acodec=ac3:mv0:nr=10"
 ##
 ### AUDIO
 AUD="lavc"      # -oac
 AUDOPT=""

With this i get records in a good quality, a bit big size and moderate
cpu usage.

Next step is: reduce file size, improve quality.  Watching the recorded
video on tv, which is much worse than my pc monitor, is ok but on pc
(full screen scaling) there are edges, flicker,...  

So i reencode the video later on a faster pc after recording where i
must not care about real time things:

-vf pp=de,scale=704:544,denoise3d -oac copy 
-ovc lavc -lavcopts vcodec=mpeg4:mbd=1:aspect=4/3 -sws 1
-ffourcc divx

With this second process i got a video with "good" quality, low size.

And here i have some questions:
	a) scaling the low source video to a bigger size, isn't this not
	something like "interpoling" by low-budget scanners? My thought
	was that software scaling may have a better quality then later
	scaling in real time by hardware?

	b) Are there filters,one/two pass runs or any other
	parameters,things you would do? I tested a lot but mostly i do
	not see a real difference.

	c) The -ffourcc option. Is it correct that lavc with
	vcodec=mpeg4 produce a divx coded video? All my linux player
	accepted the coded videos but on a friends windows pc (with vlc
	player) it wouldn't play. Only until i use the above -ffourcc
	with divx or DX50 he could play it. So: is this option rather a
	cosmetic entry in the header or do i really change the codec by
	setting/changing this parameter?

My solution B and my actual solution:

My thougt was: as better the source materials resolution then the
rescaled video is also better, nevertheless if i do this by software or
hardware.

Solution B record parameters)
##
### TV
TV="driver=v4l2:device=/dev/video:input=1:amode=1"
TVOPT=":mjpeg:decimation=1:quality=80:width=544:height=408"

# ------------ OUTPUT --------------------#
##
### VIDEO
VID="lavc"      # -ovc
VIDOPT="-lavcopts
vcodec=mjpeg:mbd=1:aspect=4/3:abitrate=128:acodec=ac3:mv0:nr=10"
##

With this i get a 544x408 video and this resolution is about the max
what my pc could record without overfulled video buffer.

This source material could i reencode as above to divx plus filters. I
think rescaling produces a very better result than the result from
solution A. Or BTW i don't need rescaling anymore. Especially watching
on pc is much better.

So: actually i am pleased with this concept. And yes, after seeing that
a newbie like me could get good results i thought about buying a DVD
card.

But i'm curious about getting some hints to do it better or in an other
way.

Greetings
	Gerhard