Sunday, February 17, 2013

Motion-Jpeg compression

Motion-Jpeg (MJPEG) is the video compression format that the DraCo uses when capturing and editing footage.

It basically works by compressing each video frame as a jpeg image (a second of video has between 24 to 30 frames per second depending on the video norm used). Its major advantage was that it did not require a lot of processing power from the host device to capture and manipulate this format. Its biggest flaw is that it uses lossy compression, so depending on the compression ratio used, some blockiness may be visible.

A big advantage of this format is that it is still being used a lot in networked enviroments and security facilities due to its tolerance on degraded streams and faulty conections. A packet lost of MJPEG still permits any suitable player to continue playing the original video feed without further fuss, unlike some modern compression codecs that rely on previous images to continue reproducing video.

Other advantages are the openess and simple nature of their encoders and decoders, unlike for example, H.264, VTASC, etc.

On the downside, there is lot of room for improvement in the compression concept of this codec, for both being lossy, which results in its reduced video quality, and for not achieving the immensely high compression rates we witness nowadays.

Every video codec we have nowadays, is only good certain tasks. There is no ideal one. They all have their strengths and weaknesses.As they say, in the end, beauty is in the eye of the beholder.

Wednesday, February 6, 2013

From DraCo to Cassie

The DraCo was not a comercial success, but that didnt stop MacroSystem. They took the DraCo and redesigned it to make it more affordable and easier to use for common people that had no Amiga knowledge. In fact, the DraCo was the development box used to program the software for what would be called the Casablanca, now known as the Casablanca Classic.

The first thing they did in this new design called "Casablanca", was to drop Amiga compatibility, whilst retaining and heavily modifying AmigaOS to suit their new standalone NLE hardware. The Amiga workbench was now, never again available, you were directly taken to the video editing suite (a deeply enhanced and modifyed Movieshop) which was called System Software.

The filesystem was changed for a custom developed one, to ensure users wont pry, accidentally harm or pirate software. In fact, a couple of hardware and software protection schemes were devised to discourage piracy, such as unique id hardware number, and floppy hardware id track that checked floppies to prevent the interchange between systems.

A 2x20 char LCD was placed on the front of the Casablanca to display status messages. This LCD was driven by the parallel port lines, whilst a real parallel port was never implemented.

A FireWire connector was mounted but required the optional DV module to become active, which was very similar to the one that was available for the DraCo.

Zorro II and DraCo Direct slots were absent in this new design. Also, the maximum system memory was reduced to 32MB available in only 2 sockets (the DraCo had 4 sockets that could together hold a total of 128MB).

The Altais graphics card was removed completely,  making place for a DraCo Motion integrated framebuffer solution that pushed its frames thru the video outputs.

Furthermore, MacroSystem decided to change the main processor they were using, for a low cost version of either the 68040 or 68060 which offered the same performance, but with less features (no MMU and no FPU).

In the end, the "Cassie" as it was affectionaly adressed by its users, was a top seller for MacroSystem. They sold more than 45,000 units and the company grew exponentially.

http://www.macrosystem.be/afbeeldingen/casa1.jpg

Summary of changes between the DraCo and the Casablanca:


Item DraCoVision Casablanca
Numebr of PCB boards 4 2
Casework Yeong Yang cube server Low profile rack (VCR style)
Power Supply AT 230 watts built-in low wattage without case
CPU 68060RC50 68LC060 or 68LC040V
Simm sockets 4 2
Max RAM 128 MB 32 MB
CIA´s sockets 2 None
Draco Motion CVBS output Yes None
Graphics card Yes, Altais None, integrated into Draco Motion´s video output
Hardware floppy copy protection None Yes
Zorro II Amiga compatible slots 5 None
DraCo Direct slots 4 None
Front mini LCD (2x20 characters) None Yes (parallel port driven)
Status leds in front panel Yes, 8 leds None