robert@eva.slu.se (Robert Olsson datoravd, EMC tfn 018-172581) (08/27/88)
Has anybody made an implementation of the codes in the CCITT T.4 telefax recommendation. I think it's called modified Huffman code and is used to compress scanned images in facsimile machines. I've stared at codes for some time now and may be capable of encoding from run lengths to Huffman codes - but decoding Huffman codes into run lengths ? To do that I would definitely need the algorithm. Where can I find it ? Or code? Robert Olsson Swedish university of agricultural sciences
robert@eva.slu.se (Robert Olsson datoravd, EMC tfn 018-172581) (08/27/88)
[ This message was cross-posted to comp.lang.c and comp.dcom.modems. ] [ I am placing it only in comp.dcom.telecom. -chip ] Has anybody made an implementation of the codes in the CCITT T.4 telefax recommendation. I think it's called modified Huffman code and is used to compress scanned images in facsimile machines. I've stared at codes for some time now and may be capable of encoding from run lengths to Huffman codes - but decoding Huffman codes into run lengths ? To do that I would definitely need the algorithm. Where can I find it ? Or code? Robert Olsson Swedish university of agricultural sciences
efb@ames.arc.nasa.gov (Everett F. Batey II) (08/28/88)
In article <telecom-v08i0134m07@vector.UUCP> robert@eva.slu.se (Robert Olsson datoravd, EMC tfn 018-172581) writes: >X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) > >Has anybody made an implementation of the codes in the CCITT T.4 telefax There are many ( software and hardware ). Unicon ( suned1!unicon!psc@elroy.JPL .NASA.Gov did ours. I STRONGLY urge you invest in the CCITT Red Book, in english from some outfit in Vienna, VA, USA. Or find your government rep to the CCITT for local availability. There are many qualities of implementations of Gp IV, 6X to 40X or better of compression and seconds to minutes to do the lookups. It appears the standard may be partly implemented ( like Gp III ) or VERY FULLY, MUCH better but slower. This is a LOT of work to implement. -- suned1!efb@elroy.JPL.Nasa.Gov sun!tsunami!suned1!efb efbatey@NSWSES.ARPA Any statements / opinions made here are mine, alone, not those of the United States, the DoD, the Navy, the Congress, the Judiciary, nor ...