Can't install OpenCV with ffmpeg

[rkcarroll]

Package: opencv:x64-windows
Vcpkg version: 2018.10.20-nohash

from ...\vcpkg\buildtrees\opencv\config-x64-windows-out.log

-- FFMPEG: Download: opencv_ffmpeg.dll
CMake Error at cmake/OpenCVDownload.cmake:158 (message):
Downloads are not permitted during configure. Please pre-download the file "E:/Libs/vcpkg/downloads/opencv-cache/ffmpeg/fa5a2a4e2f37defcb95bde8ed145c2b3-opencv_ffmpeg.dll":

  vcpkg_download_distfile(OCV_DOWNLOAD
      URLS "https://raw.githubusercontent.com/opencv/opencv_3rdparty/8041bd6f5ad37045c258904ba3030bb3442e3911/ffmpeg/opencv_ffmpeg.dll"
      FILENAME "opencv-cache/ffmpeg/fa5a2a4e2f37defcb95bde8ed145c2b3-opencv_ffmpeg.dll"
      SHA512 0
  )

Call Stack (most recent call first):
3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
cmake/OpenCVFindLibsVideo.cmake:228 (download_win_ffmpeg)
CMakeLists.txt:635 (include)

-- Configuring incomplete, errors occurred!

The file that is actually cached on my machine is: b8120c07962d591e2e9071a1bf566fd0-opencv_ffmpeg.dll

[evolv-bricerive]

I had the same issue.
Looks like a checksum mismatch.
As a workaround, I patched the expected checksums in

...\vcpkg\buildtrees\opencv\src\3.4.3-187d3dc39b\3rdparty\ffmpeg\ffmpeg.cmake

replaced

ocv_update(FFMPEG_FILE_HASH_BIN32 "fa5a2a4e2f37defcb95bde8ed145c2b3")
ocv_update(FFMPEG_FILE_HASH_BIN64 "2cc08fc4fef8199fe80e0f126684834f")

by

ocv_update(FFMPEG_FILE_HASH_BIN32 "b8120c07962d591e2e9071a1bf566fd0")
ocv_update(FFMPEG_FILE_HASH_BIN64 "dc9c50e7b05482acc25d6ce0ac61bf1d")

Got the correct checksums from the download directory:

...\vcpkg\downloads\opencv-cache\ffmpeg

[rkcarroll]

Great! Thanks for tracking down where the hash gets specified.

[NancyLi1013]

@rkcarroll, thanks for posting this issue. Could you help us confirm whether this issue still exists on your machine now? I cannot reproduce it. If it is still a problem for you, please help us provide more info about this, such as the steps to reproduce or something special on your test environment. If not, please help to close this issue. Thank you very much.

[bricerive]

I believe the current version has the proper hash values in
vcpkg\buildtrees\opencv\src\3.4.3-701a6234df\3rdparty\ffmpeg\ffmpeg.cmake

So the issue is gone.

[NancyLi1013]

@bricerive, thanks for your feedback. I noticed that the current version hash values are still the same as that before:
ocv_update(FFMPEG_FILE_HASH_BIN32 "fa5a2a4e2f37defcb95bde8ed145c2b3")
ocv_update(FFMPEG_FILE_HASH_BIN64 "2cc08fc4fef8199fe80e0f126684834f")
So I'm confused that why this issue cannot be reproduced now. Do you have any other suggestions?

[bricerive]

I beleive it is because they now match the hash in
...\vcpkg\downloads\opencv-cache\ffmpeg:
fa5a2a4e2f37defcb95bde8ed145c2b3-opencv_ffmpeg.dll
2cc08fc4fef8199fe80e0f126684834f-opencv_ffmpeg_64.dll

[NancyLi1013]

@bricerive, thanks a lot for your clear clarification. I understand it now.