ffmpeg software decoder implementation (#461)

* WIP: ffmpeg based software decoder

* minor update

* WIP: FFMpeg SW decoder support

* FFMpeg decoder working version

* working version without threading

* multithreading working with FFMpeg decoder

* moved ffmpeg decoder to separate folder

* updated changelog

* minor change

* resolved review comments

* resolved review comments

---------

Co-authored-by: Lakshmi Kumar <lakshmi.kumar@amd.com>

[ROCm/rocdecode commit: 52eb62fabf]

projects/rocdecode/api/rocdecode.h

@@ -107,6 +107,9 @@ typedef enum rocDecVideoSurfaceFormat_enum {
     rocDecVideoSurfaceFormat_YUV444 = 2,       /**< Planar YUV [Y plane followed by U and V planes] */
     rocDecVideoSurfaceFormat_YUV444_16Bit = 3, /**< 16 bit Planar YUV [Y plane followed by U and V planes].
                                                 Can be used for 10 bit(6LSB bits 0), 12 bit (4LSB bits 0) */
+    rocDecVideoSurfaceFormat_YUV420 = 4,       /**< Planar YUV [Y plane followed by U and V planes in 4:2:0 format] */
+    rocDecVideoSurfaceFormat_YUV420_16Bit = 5, /**< 16 bit Planar YUV [Y plane followed by U and V planes in ].
+                                                Can be used for 10 bit(LSB), 12 bit (LSB) */
 } rocDecVideoSurfaceFormat;
 
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