fix ffv1 color/alpha shift (#581)

* Add 'gbra' to alpha channel regex check

* Add input color depth 16bit option to ffv1-mkv.json

* use rgba64le by default in ffv1-mkv.json

video_formats/ffv1-mkv.json

@@ -8,10 +8,11 @@
         "-g", ["gop_size", "INT", {"default": 1, "min": 1, "max": 300, "step": 1}],
         "-slices", ["slices", ["4", "6", "9", "12", "16", "20", "24", "30"], {"default": "16"}],
         "-slicecrc", ["slicecrc", ["0", "1"], {"default": "1"}],
-        "-pix_fmt", ["pix_fmt", ["bgra", "rgba64le", "yuv420p", "yuv422p", "yuv444p", "yuva420p", "yuva422p", "yuva444p", "yuv420p10le", "yuv422p10le", "yuv444p10le", "yuv420p12le", "yuv422p12le", "yuv444p12le", "yuv420p14le", "yuv422p14le", "yuv444p14le", "yuv420p16le", "yuv422p16le", "yuv444p16le", "gray", "gray10le", "gray12le", "gray16le"], {"default": "bgra"}]
+        "-pix_fmt", ["pix_fmt", ["rgba64le", "bgra", "yuv420p", "yuv422p", "yuv444p", "yuva420p", "yuva422p", "yuva444p", "yuv420p10le", "yuv422p10le", "yuv444p10le", "yuv420p12le", "yuv422p12le", "yuv444p12le", "yuv420p14le", "yuv422p14le", "yuv444p14le", "yuv420p16le", "yuv422p16le", "yuv444p16le", "gray", "gray10le", "gray12le", "gray16le"], {"default": "rgba64le"}]
     ],
     "audio_pass": ["-c:a", "flac"],
     "save_metadata": ["save_metadata", "BOOLEAN", {"default": true}],
     "trim_to_audio": ["trim_to_audio", "BOOLEAN", {"default": false}],
+    "input_color_depth": "16bit",
     "extension": "mkv"
-}
+}

videohelpersuite/load_video_nodes.py

@@ -201,7 +201,7 @@ def ffmpeg_frame_generator(video, force_rate, frame_load_cap, start_time,
                 fps_base = float(fps_match.group(1))
             else:
                 fps_base = 1
-            alpha = re.search("(yuva|rgba|bgra)", line) is not None
+            alpha = re.search("(yuva|rgba|bgra|gbra)", line) is not None
             break
     else:
         raise Exception("Failed to parse video/image information. FFMPEG output:\n" + lines)