VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Wed Apr 05 2023 - 23:05:51 CDT

Hi,
  While is almost certainly possible to directly send frames into a video
encoder like ffmpeg (e.g., by writing a frame sequence to a unix domain
socket, named pipe, or similar input mechanism), it likely wouldn't buy
you significant performance gain, and you'd lose the ability to
do multi-pass encoding, since the video encoder couldn't "rewind"
and retry encoding frame sequences that create bitrate
control or allocation challenges.
Multi-pass video encoding yields the highest overall quality vs. bit rate,
but encoders that support this need to be able to random access the input.
For a long movie sequence, the input can be quite large (far too much
to hold in RAM).

Regarding APNG: Looking around at the mainstream PNG encoders or decoders
that I've used in the past, none of them seem to support APNG yet.
There's a couple of unofficial APNG patches floating around for libpng
if you felt really motivated to hack in support.

Best,
  John

On Wed, Apr 05, 2023 at 03:08:10PM -0500, Diego Gomes wrote:
> Hi fellows,
> while making a video today I got myself wondering...
>
> Has anyone ever come up with a way to render VMD frames straight to a video
> encoder?
>
> I was also hoping for a secret implementation of APNG in ImageIO.c ... not
> my lucky day :/
>
> Best,
> Diego.
>
> --
> Diego Enry B. Gomes, PhD
> Department of Physics
> Leach Science Center
> Auburn University
> dgomes_at_auburn.edu 

-- 
Research Affiliate, NIH Center for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
http://www.ks.uiuc.edu/~johns/           
http://www.ks.uiuc.edu/Research/vmd/