obs-ffmpeg: Add FFmpeg format -> obs format func

plugins/obs-ffmpeg/obs-ffmpeg-formats.h

@@ -25,6 +25,21 @@ static inline enum AVPixelFormat obs_to_ffmpeg_video_format(
 	return AV_PIX_FMT_NONE;
 }
 
+static inline enum video_format ffmpeg_to_obs_video_format(
+		enum AVPixelFormat format)
+{
+	switch (format) {
+	case AV_PIX_FMT_YUV420P: return VIDEO_FORMAT_I420;
+	case AV_PIX_FMT_NV12:    return VIDEO_FORMAT_NV12;
+	case AV_PIX_FMT_YUYV422: return VIDEO_FORMAT_YUY2;
+	case AV_PIX_FMT_UYVY422: return VIDEO_FORMAT_UYVY;
+	case AV_PIX_FMT_RGBA:    return VIDEO_FORMAT_RGBA;
+	case AV_PIX_FMT_BGRA:    return VIDEO_FORMAT_BGRA;
+	case AV_PIX_FMT_NONE:
+	default:                 return VIDEO_FORMAT_NONE;
+	}
+}
+
 static inline enum audio_format convert_ffmpeg_sample_format(
 		enum AVSampleFormat format)
 {