The first question is why?
Why would a company wrap up a h264/AVC camera stream inside the ASF container format? I dont think its the best partnership and even upon research, the general consensus appears to be that its problematic.
The player interface is a very common one. It has been rebranded by a few companies and has a few different colour variations. A few linked file extensions are .dav, .dev, .mpg, .mp4 …and now .asf!
If you were greeted with a disk full of .asf extended files only then you could easily mistake them for wmv format videos. These are the common type used within the .asf container. However, when taking a closer look, they are not – they are h264 streams. And what does the pixel size say above – 704 x 576.
Wrong – the raw streams are 352 x 576!
After doing the usual Forensic File Analysis with Mediainfo, FFprobe etc it was time to attempt a rewrap of these files.
What I found worked best was to extract the stream as a raw h264 first and then place this into an avi. For some reason ffmpeg wouldn’t do it correctly in one hit.
The other thing to look for is the small ‘avi’ button at the bottom of the player. It is possible to re stream the asf file into a .dav file. This file will then play in another version of the player that has the ‘avi’ button enabled. The problem with this is that you cant see what is going on and what is happening to the footage.
Re-wrapping these files was mainly an exercise to assess what was going on within the file due to the frame size issue. Even if you export a frame from within the player it comes out at 704 x 576. For me, I would prefer to get the raw unadulterated frame from within the h264 stream and then assess which resizing filter is best from within Photoshop.
I’m the one doing the resizing then – and not the player.
A few links on wikipedia: