Possible free Mpeg2 HD encoder for Mac

[Paul Mogg]

I've posted about this before, but If anyone is interested in a virtually free MPEG2 encoder that wil encode HDTV material, someone over at the ffmpegx forum recently told me that you can take the shareware Mpeg2enc encoder (that is usually controlled from the ffmpegx GUI) and make minor changes to a few of the command line arguments, and it will encode HD. The exact parameters he said to change are listed below if anyone is interested in trying it. Please post if you are successful, or if you have already tried and found a solution, as I think this would be of interest to a great many people who would like to edit their HD material. I intend to try myself, but don't have much free time to spend on this right now.
He also mentioned that on the PC, the $60 shareware MPEG2 encoder called "tmpgenc" will encode HD right off the shelf, with excellent results.

All the best


set to 4

Code:
/* Level ID */

Specifies coded parameter constraints, such as bitrate, sample rate, and maximum allowed motion vector range.

Code Meaning Typical use ---- --------------- ----------------------------------------------- 4 High Level HDTV production rates: e.g. 1920 x 1080 x 30 Hz 6 High 1440 Level HDTV consumer rates: e.g. 1440 x 960 x 30 Hz 8 Main Level CCIR 601 rates: e.g. 720 x 480 x 30 Hz 10 Low Level SIF video rate: e.g. 352 x 240 x 30 Hz




set to 512 (for 19.2meg/s standard 720p)

Code:
/* vbv_buffer_size (in multiples 16 kbit) */

Specifies, according to the Video Buffering Verifier decoder model, the size of the bitstream input buffer required in downstream decoders in order for the sequence to be decoded without underflows or or overflows. You probably will wish to leave this value at 112 for MPEG-2 Main Profile at Main Level, and 20 for Constrained Parameters Bitstreams MPEG-1.



set to 2 for DC_P

Code:
/* intra_dc_precision */

Specifies the effective precision of the DC coefficient in MPEG-2 intra coded macroblocks. 10-bits usually achieves quality saturation.

Code Meaning ---- ----------------- 0 8 bit 1 9 bit 2 10 bit 3 11 bit



set to all 24's (or 32's) except for position 1 which must be a 8 (you will need to build a table they explain (simple))


Code:
/* name of intra quant matrix file ("-": default matrix) */

Setting this to a value other than - specifies a file containing a custom intra quantization matrix to be used instead of the default matrix specified in ISO/IEC 13818-2 and 11172-2. This file has to contain 64 integer values (range 1...255) separated by white space (blank, tab, or newline), one corresponding to each of the 64 DCT coefficients. They are ordered line by line, i.e. v-u frequency matrix order (not by the zig-zag pattern used for transmission). The file intra.mat contains the default matrix as a starting point for customization. It is neither necessary or recommended to specify the default matrix explicitly.

Large values correspond to coarse quantization and consequently more noise at that particular spatial frequency.

For the intra quantization matrix, the first value in the file (DC value) is ignored. Use the parameter intra_dc_precision (see below) to define the quantization of the DC value.





use default (all 16's):


Code:
/* name of non intra quant matrix file ("-": default matrix) */

This parameter field follows the same rules as described for the above intra quant matrix parameter, but specifies the file for the NON-INTRA coded (predicted / interpolated) blocks. In this case the first coefficient of the matrix is NOT ignored.

The default matrix uses a constant value of 16 for all 64 coefficients. (a flat matrix is thought to statistically minimize mean square error). The file inter.mat contains an alternate matrix, used in the MPEG-2 test model.
__________________
Paul

[Chris Hurd]

Fascinating stuff -- anyone tried this yet?