MPEG compressors

Introduction

Cleaner (formerly known as Media Cleaner Pro) has established itself as the leading video-compression software. It allows digital-video producers, Web developers and multimedia designers to compress video into a number of different formats – such as QuickTime, AVI, RealMedia and MPEG – and optimize it for playback on a wide range of media, including broadcast, CD, DVD and online. By default, Cleaner features rudimentary support for two flavours of MPEG video compression – MPEG-1 and MPEG-2. MPEG-1 is a full frame-rate video-compression format with a data rate typically of 400K per second (Kbps), and is typically compressed at quarter size – for example, 352-x-288 pixels for PAL – or at smaller sizes for Web delivery. It can be played back on a desktop computer using QuickTime or Windows Media Player, and is often used instead of QuickTime .MOV files on multimedia projects. MPEG-2 utilizes a much higher data rate of around 6Mbits per second, and encodes at full screen size – for example, 720-x-576 for PAL at broadcast quality – and full frame rate (24-30fps). It’s used mainly for DVD, and requires special hardware acceleration for playback on a desktop computer. Charge forward
Cleaner 5’s default support for these formats gives you little control over the data rate or other output options of either format, though for most users this will be sufficient. What MPEG Charger does is extend Cleaner’s functionality and add a greater level of flexibility to MPEG-1 and MPEG-2 compression. MPEG Supercharger works only with MPEG-2 files, and includes a PCI card that accelerates the MPEG-2 compression from within Cleaner. With Charger installed, Cleaner works in virtually the same way, except that now there are a few more options in the Advanced Settings when compressing either MPEG-1 or MPEG-2. Clicking the Image tab will allow you to determine the dimensions of the compressed file, and choose an aspect ratio, such as 4:3 for PAL or NTSC, or square pixels. MPEG pixels are not always square for DVD playback, so this can get quite complex. However, this added feature means that professional MPEG-developers can now use Cleaner for encoding footage for DVD. The greatest flexibility that Charger gives though, is with encoding options. Whereas in Cleaner you had to accept the defaults, with Charger you can set a particular data rate, and this can be a constant data-rate (CDR) or what is called one- or two-pass Variable Bit Rate (VBR). You can also alter what is called the Group of Pictures (GOP), and P-frame distance to change the file size and image quality – but you need to know what you’re doing here, as it’s easy to create non-standard settings that may be incompatible with certain devices. Cleaner Supercharger provides hardware acceleration for MPEG-2 encoding through a PCI card that slots into a G3 or G4 tower, as well as installation software to upgrade Cleaner 5. Given that a minute of raw footage can take about 1 hour to encode in Cleaner, if you do a lot of MPEG-2 encoding any help is valuable. With the card installed, encoding times are slashed to a quarter, thanks to the dedicated encoding chip. Serious users will want to use Media 100’s MediaPress product for real-time encoding. But that’s all Supercharger does – it would’ve been useful if the Supercharger card also worked as an MPEG playback card, so you could actually preview the MPEG-2 files created. For MPEG-2 playback, Wired makes a high-end hardware decoder called WiredStream. Neither does Supercharger give any of the MPEG-1 features of Charger, which means you’ll still need Charger for MPEG-1 options.
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