[FFmpeg-trac] #7600(avcodec:new): Add lossless option to libaom-av1

[FFmpeg]

#7600: Add lossless option to libaom-av1
-------------------------------------+-----------------------------------
             Reporter:  Ewout        |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  libaom       |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-----------------------------------

Comment (by Ewout):

 I did the following test:
 1. Encoded a .png screenshot to .png with FFmpeg
 2. Encoded this screenshot to a AV1 with `-c:v libaom-av1 -cpu-used 0`,
 once with `-lossless 1` and once without.
 3. Encoded these .mp4's back to .png's
 4. Repeated step 2 and 3 once more.

 This resulted in 5 .png's, the input and two output files from both the
 lossy and lossless.
  - Input: 185.760 bytes
  - Lossless Round 1: 171.312 bytes
  - Lossless Round 2: 171.312 bytes
  - Lossy Round 1: 263.532 bytes
  - Lossy Round 2: 249.829 bytes

 There were also 4 MP4's generated in the process:
  - Lossless Round 1: 59.061 bytes
  - Lossless Round 2: 59.061 bytes
  - Lossy Round 1: 11.260 bytes
  - Lossy Round 2: 11.064 bytes

 Where the lossy files are losing data, the lossless files aren't. I also
 used [https://www.diffchecker.com/image-diff diffchecker] to check for
 difference between the input and output png's, the lossy showed a
 difference while the lossless didn't. Looks like it works great and can be
 merged.

 All files and the commands used can be found here:
 https://mega.nz/#F!W24HjSjJ!Z266_XE4Ln4KTmP3ZOR4GA

 Small note: Line 33 misses a comma at the end.
 {{{
 { "lossless",         "Lossless mode",
 OFFSET(lossless),       AV_OPT_TYPE_BOOL, {.i64 = 0},  0, 1, VE}
 }}}
 Thanks to [https://www.reddit.com/user/MrSmilingWolf u/MrSmilingWolf] for
 the Windows build and spotting the missing comma.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7600#comment:10>
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