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client API: note about libswscale corrupting memory 

The software rendering API makes libswscale directly write into supplied
user memory. As such, weird memory corruption bugs on non-optimal buffer
configurations are exposed to the user.
This commit is contained in:
wm4 2020-08-20 20:37:17 +02:00
parent 30dcfbc9cb
commit b16a6cb6c6
1 changed files with 10 additions and 1 deletions
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11
libmpv/render.h
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@ -390,7 +390,13 @@ typedef enum mpv_render_param_type {
* target surface. It must be a multiple of the pixel size, and have space
* for the surface width as specified by MPV_RENDER_PARAM_SW_SIZE.
*
* It should be a multiple of 64 to facilitate fast SIMD operation.
* It should be a multiple of 64 to facilitate fast SIMD operation. Lower
* alignment might trigger slower code paths. In addition, it appears that
* if libswscale is used, stride must be at least a multiple of 16, or
* libswscale may randomly corrupt memory. The API still accepts unaligned
* values, because libswscale is not supposed to corrupt memory, and whether
* it does depends on its implementation details and bugs. If mpv is built
* with zimg (and zimg is not disabled), no problems should occur.
*/
MPV_RENDER_PARAM_SW_STRIDE = 19,
/*
@ -407,6 +413,9 @@ typedef enum mpv_render_param_type {
* will do it anyway). It is assumed that even the padding after the last
* line (starting at bytepos(w, h) until (pointer + stride * h)) is
* writable.
*
* It should be a aligned to 64 to facilitate fast SIMD operation. Lower
* alignment might trigger slower code paths.
*/
MPV_RENDER_PARAM_SW_POINTER = 20,
} mpv_render_param_type;