3 ms·

It is amazing that it is still possible to optimize the compression algorithm for JPEG, a file format that is already over 20 years old.

fiatmoney 13y ago
It sounds like he didn't optimize the algorithm per se; he optimized the implementation of the algorithm for the particular processor. Still very impressive.
- vonseel 13y ago
  "Having developed a blazing fast DCT implementation, Huffman then became a bottleneck. We innovated on that portion with tight hand-tuned assembly code that leverages special features of the ARM processor instruction set to make it as fast as possible.” I understood he first optimized the algorithm, then tuned it to be even faster on ARM?
  - huxley 13y ago
    I read it as saying that, after optimizing the DCT (lossy) compression as much as he could, he focused on the Huffman (lossless) encoding phase which gave him further optimization opportunities.
zafka 13y ago
I was amazed the first several times I saw things i thought where old as dirt have amazing improvements made. One of the first was about 10 years ago, when a friend made improvements on lighting ballasts in conjunction with solar work. Now I try to keep my eyes open for these opportunities.
jmspring 13y ago
The actual standard allows for a variety of options around how the compression portion is handled -- there is the baseline mode and then options for custom huffman tables, etc. The best source for the JPEG Standard -- http://www.amazon.com/JPEG-Compression-Standard-Multimedia-Standards/dp/0442012721 http://www.amazon.com/JPEG-Compression-Standard-Multimedia-S... My memory is a bit fuzzy here, but from what I recall, a friend tried implementing JPEG compression on a parallel system (back in the mid 90s). One of the trouble spots was the reliance on the relationship between blocks regarding prediction of the DC coefficient. One startup I worked at, we had an entropy encoding method that could add 20-30% additional compression just by recording coefficients. Patent here -- http://www.google.com/patents/US6236762 http://www.google.com/patents/US6236762
raverbashing 13y ago
I'm not so sure about it, but lossy compression algorithms are usually "non deterministic" and what I mean by that is that there is a target format to encode to, but you have some variation in how you're turning the original data into that So there's a lot of room in optimising the process

fiatmoney 13y ago

It sounds like he didn't optimize the algorithm per se; he optimized the implementation of the algorithm for the particular processor. Still very impressive.

vonseel 13y ago
"Having developed a blazing fast DCT implementation, Huffman then became a bottleneck. We innovated on that portion with tight hand-tuned assembly code that leverages special features of the ARM processor instruction set to make it as fast as possible.” I understood he first optimized the algorithm, then tuned it to be even faster on ARM?
- huxley 13y ago
  I read it as saying that, after optimizing the DCT (lossy) compression as much as he could, he focused on the Huffman (lossless) encoding phase which gave him further optimization opportunities.

zafka 13y ago

I was amazed the first several times I saw things i thought where old as dirt have amazing improvements made. One of the first was about 10 years ago, when a friend made improvements on lighting ballasts in conjunction with solar work. Now I try to keep my eyes open for these opportunities.

jmspring 13y ago

The actual standard allows for a variety of options around how the compression portion is handled -- there is the baseline mode and then options for custom huffman tables, etc. The best source for the JPEG Standard -- http://www.amazon.com/JPEG-Compression-Standard-Multimedia-Standards/dp/0442012721 http://www.amazon.com/JPEG-Compression-Standard-Multimedia-S... My memory is a bit fuzzy here, but from what I recall, a friend tried implementing JPEG compression on a parallel system (back in the mid 90s). One of the trouble spots was the reliance on the relationship between blocks regarding prediction of the DC coefficient. One startup I worked at, we had an entropy encoding method that could add 20-30% additional compression just by recording coefficients. Patent here -- http://www.google.com/patents/US6236762 http://www.google.com/patents/US6236762

raverbashing 13y ago

I'm not so sure about it, but lossy compression algorithms are usually "non deterministic" and what I mean by that is that there is a target format to encode to, but you have some variation in how you're turning the original data into that So there's a lot of room in optimising the process