Fix scaling of bitmap subs when the corresponding video is cropped (#2670).

[dcpomatic.git] / src / lib / ffmpeg_decoder.cc

diff --git a/src/lib/ffmpeg_decoder.cc b/src/lib/ffmpeg_decoder.cc
index 6e9d671a2fa87792e2ea5b58d6b2d9b2e136822c..dcad184fa81ea17ea3ddc5e4a0cdf7b9052984db 100644 (file)
--- a/src/lib/ffmpeg_decoder.cc
+++ b/src/lib/ffmpeg_decoder.cc
@@ -781,11 +781,23 @@ FFmpegDecoder::process_bitmap_subtitle (AVSubtitleRect const * rect)
        if (target_height == 0 && video_codec_context()) {
                target_height = video_codec_context()->height;
        }
-       DCPOMATIC_ASSERT (target_width);
-       DCPOMATIC_ASSERT (target_height);
+
+       int x_offset = 0;
+       int y_offset = 0;
+       if (_ffmpeg_content->video && _ffmpeg_content->video->use()) {
+               auto const crop = _ffmpeg_content->video->actual_crop();
+               target_width -= crop.left + crop.right;
+               target_height -= crop.top + crop.bottom;
+               x_offset = -crop.left;
+               y_offset = -crop.top;
+       }
+
+       DCPOMATIC_ASSERT(target_width > 0);
+       DCPOMATIC_ASSERT(target_height > 0);
+
        dcpomatic::Rect<double> const scaled_rect (
-               static_cast<double>(rect->x) / target_width,
-               static_cast<double>(rect->y) / target_height,
+               static_cast<double>(rect->x + x_offset) / target_width,
+               static_cast<double>(rect->y + y_offset) / target_height,
                static_cast<double>(rect->w) / target_width,
                static_cast<double>(rect->h) / target_height
                );