Software versus Hardware Encoding

So, now we know that Variable Bit Rate encoding is the solution to all our problems, right?  Well... sort of.  VBR provides a set of mathematical tools that can be used to create higher quality video.  Unfortunately, just as in other aspects of life, some people use the available tools better than others.  That's one reason some cars (for example) cost more than others.  In this case, the people using the tools are those who develop the encoder (software or hardware) as well as those who use the encoder.  Failure on the part of either to do their job well will diminish the quality of your video

There are two techniques used for encoding video.  One uses specialized hardware to encode video, usually at the same speed at which the video itself is played.  This approach is known as real-time encoding.  Most hardware encoders use constant bit rate (CBR) encoding because it's easier to implement, and the hardware can be sold for less, thus appealing to a broader market.  Some, generally more expensive hardware encoders, use VBR encoding.

Software encoders are used as part of a more time consuming two-part process.  In the first part, the video is digitized ('captured') to a hard drive.  This takes the same amount of time as the entire hardware encoding process described above.  In the second part, the software encoder encodes the video.  This may take many times the length of the video to complete, depending on how well the encoder software is written and the encoding options selected.  Most software encoders can handle both CBR and VBR encoding.

That sounds pretty straight-forward, doesn't it?  If hardware encoders can produce VBR-encoded video and run many times faster than software encoders, surely that must  be the right solution.  Isn't it?

Multi-Pass VBR Encoding

Of course not!  Nothing in this business is as simple as it seems at the outset.  As I mentioned on the MPEG Encoders page, a much more intelligent mathematical algorithm is required to produce good VBR encoding.  The need to do this in real-time puts an enormous burden on a hardware encoder, so the price of a very good hardware encoder can be $20,000 or more.  Less expensive hardware encoders use a simpler, less costly approach to VBR, and the results show it (see the comments about 'pixelization' and 'quantization effects' on the MPEG Encoders page).

This is where software encoders shine; though they take longer to encode than a hardware encoder, they have the luxury of going back through the encoded video repeatedly (i.e., multiple passes).  In each pass, the software encoder compares the encoded video to the original video and makes adjustments to the bit allocation to improve the match between the two.  This is known as multi-pass VBR encoding.  It is the most time-consuming approach to MPEG encoding, but when done well, consistently produces outstanding results.

So, at last we have the final solution - multi-pass variable bit rate encoding.  But wait; as I said above, the DVD business is never that simple.  Note that in the last paragraph, I said "when done well".  That's the rub.  There are lots of software MPEG-2 encoders available, some of do multi-pass VBR, but very, very few of which do it well.

The Best Multi-Pass VBR Software Encoder

This is easy.  I've evaluated many encoders (hardware & software), corresponded with those who owned them, and found only one product that consistently produces great 2 hour DVDs with any video content I've thrown at it, and that's Cinema Craft SP.  Unless your DVD transfer company uses this encoder in 3-pass VBR mode or reviews each and every second of your DVD for encoding errors before shipping it to you, I'd take my business somewhere else.

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