On Sun, Jan 06, 2019 at 12:57:37PM +0100, Carl Eugen Hoyos wrote: > 2019-01-06 12:12 GMT+01:00, Peter Ross <pr...@xvid.org>: > > for the '127-bit shift left' algorithm to work as intended, little-endian > > reads and writes must be used. > > > Why not using AV_WL64() and and AV_RL64()?
good question. > Is there a measurable speed difference? x86: no difference, compiler output is identical. other cpus that do not support unaligned reads: big difference, due to the compiler inserting additional instructions to check the alignment of the data. mipsel: RN64A: bench: utime=105.902s stime=0.040s rtime=105.933s RN64: bench: utime=230.055s stime=0.004s rtime=230.082s why so much difference? the 127-bit shift left operation must happen for each 1-bit DSD sample. in a single channel of DSD audio, there are at least 2.8 millions 1-bit samples per second. -- Peter (A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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