On 2012/12/24 19:28, Fernando Cassia wrote:
On Mon, Dec 24, 2012 at 6:59 PM, Roberto Ragusa <mail@xxxxxxxxxxxxxxxx
<mailto:mail@xxxxxxxxxxxxxxxx>> wrote:
Hmmmm? Having an additional intermediate encoding to avoid re-encoding
artifacts???
By converting to very high quality MPEG2 you avoid issues with AVI, XVID, H.264
encoding and decoding which a lot of programs handle differently (you can get
different results just by using different builds of FFMPEG).
For instance, it´s impossible to do frame-accurate cutting with a lot of AVI
cutters, whereas on MPEG2 cuts are frame-perfect. Don´t ask me why, I´m not a
codecs writer just an end user of many video cutting tools. And this is based on
my personal experience.
MPEG2 is the codec used on broadcast HDTV, and while it´s much less efficient
than H.264, it´s less CPU intensive for applications to work with.
FC
Fernando, any time you edit MEPEG2, 3, 4, etc the image will degrade.
With any of the formats you can get frame accurate editing. The farther
into a GOP, group of pictures, you get the worse the image
reconstruction. Since you must recreate a reference frame, the first
frame of a GOP, you're starting with a worse image. So at least the
initial frames are likely to be somewhat "iffy".
With motion JPEG, MJPEG, editing is simpler. Each frame is a full
picture encoded. So all you do is grab the start frame and all the
other frames through the output without ever decompressing anything.
Also a few years ago a SMPTE group did some experiments with MJPEG
vs MPEG for QHD. The conclusion is that for a given bit rate the
MJPEG was at least as good as the MPEG versions they tested. (This
may have changed in recent years.)
You also want to work with at least 422 as your base editing copy.
Things like 420 have stripped out too much information that cannot
be restored except by guesswork.
{^_^} I spent several years coding this stuff as part of a
newsroom application.
--
users mailing list
users@xxxxxxxxxxxxxxxxxxxxxxx
To unsubscribe or change subscription options:
https://admin.fedoraproject.org/mailman/listinfo/users
Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
Have a question? Ask away: http://ask.fedoraproject.org
