calvore
22nd December 2002, 17:22
I decided to make myself a simply Excel Spreadsheet showing the bits per 16x16 macroblock (I didn't use 8x8 blocks, the relative values are still useful though) at various bitrates and such. I know it isn't a perfect comparison, but I use it as a good starting point to decide how much data I want to attempt to fit on a CD. Bits/macroblock work at well because they all sit around 100 range so it makes comparisons easy. I figure the more bits per macroblock, the better each individual block will look and the less artifacts.
A few things to consider before you use the numbers:
1: MPEG2 does really allocate the same amount to every macroblock, this is just an average to give you an idea.
2: Only encoding 24fps instead of 30fps (not that you really usually make a decision) is not an instant 20% savings, since if your source is truly 30 fps there is less motion betwean frames than a 24fps source and it will take less to encode each frame (in practice) but more for each second. So it is somewhere lower than 20% but still a saving.
3: Whatever else you fell like considering. Anyway, I found it to be useful if not just to recognize how much is saved (higher bits/macroblock) if you actually do an IVTC and then encode your source at 23.976 with a pulldown.
A few things to consider before you use the numbers:
1: MPEG2 does really allocate the same amount to every macroblock, this is just an average to give you an idea.
2: Only encoding 24fps instead of 30fps (not that you really usually make a decision) is not an instant 20% savings, since if your source is truly 30 fps there is less motion betwean frames than a 24fps source and it will take less to encode each frame (in practice) but more for each second. So it is somewhere lower than 20% but still a saving.
3: Whatever else you fell like considering. Anyway, I found it to be useful if not just to recognize how much is saved (higher bits/macroblock) if you actually do an IVTC and then encode your source at 23.976 with a pulldown.