Add noise to very small J2K frames (#1902).

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

diff --git a/src/lib/dcp_video.cc b/src/lib/dcp_video.cc
index 58e10f0ed69f349b65d5c51b92b89f59a872205d..cb151772700a62e661ea4dcb1f50adabf67527bb 100644 (file)
--- a/src/lib/dcp_video.cc
+++ b/src/lib/dcp_video.cc
@@ -124,15 +124,41 @@ DCPVideo::encode_locally ()
 {
        auto const comment = Config::instance()->dcp_j2k_comment();
 
-       auto enc = dcp::compress_j2k (
-               convert_to_xyz (_frame, boost::bind(&Log::dcp_log, dcpomatic_log.get(), _1, _2)),
-               _j2k_bandwidth,
-               _frames_per_second,
-               _frame->eyes() == Eyes::LEFT || _frame->eyes() == Eyes::RIGHT,
-               _resolution == Resolution::FOUR_K,
-               comment.empty() ? "libdcp" : comment
+       ArrayData enc = {};
+       int constexpr minimum_size = 65536;
+
+       auto xyz = convert_to_xyz (_frame, boost::bind(&Log::dcp_log, dcpomatic_log.get(), _1, _2));
+       while (true) {
+               enc = dcp::compress_j2k (
+                       xyz,
+                       _j2k_bandwidth,
+                       _frames_per_second,
+                       _frame->eyes() == Eyes::LEFT || _frame->eyes() == Eyes::RIGHT,
+                       _resolution == Resolution::FOUR_K,
+                       comment.empty() ? "libdcp" : comment
                );
 
+               if (enc.size() >= minimum_size) {
+                       break;
+               }
+
+               /* The JPEG2000 is too low-bitrate for some decoders <cough>DSS200</cough> so add some noise
+                * and try again.  This is slow but hopefully won't happen too often.  We have to do
+                * convert_to_xyz() again because compress_j2k() corrupts its xyz parameter.
+                */
+
+               xyz = convert_to_xyz (_frame, boost::bind(&Log::dcp_log, dcpomatic_log.get(), _1, _2));
+               auto size = xyz->size ();
+               auto pixels = size.width * size.height;
+               for (auto c = 0; c < 3; ++c) {
+                       auto p = xyz->data(c);
+                       for (auto i = 0; i < pixels; ++i) {
+                               *p = std::min(4095, std::max(0, *p + rand() % 2));
+                               ++p;
+                       }
+               }
+       }
+
        switch (_frame->eyes()) {
        case Eyes::BOTH:
                LOG_DEBUG_ENCODE (N_("Finished locally-encoded frame %1 for mono"), _index);