Merge master branch.

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

diff --git a/src/lib/util.cc b/src/lib/util.cc
index 7f370b89647557199657f47b4d47037ec5b552c0..872985024ac9a5779bfab4f9fa6fdd4988984047 100644 (file)
--- a/src/lib/util.cc
+++ b/src/lib/util.cc
@@ -26,6 +26,7 @@
 #include <iomanip>
 #include <iostream>
 #include <fstream>
+#include <climits>
 #ifdef DVDOMATIC_POSIX
 #include <execinfo.h>
 #include <cxxabi.h>
@@ -58,9 +59,11 @@ extern "C" {
 #include "dcp_content_type.h"
 #include "filter.h"
 #include "sound_processor.h"
+#include "config.h"
 
 using namespace std;
 using namespace boost;
+using libdcp::Size;
 
 thread::id ui_thread;
 
@@ -330,25 +333,100 @@ md5_digest (string file)
        return s.str ();
 }
 
-/** @param fps Arbitrary frames-per-second value.
- *  @return DCPFrameRate for this frames-per-second.
- */
-DCPFrameRate
-dcp_frame_rate (float fps)
+static bool about_equal (float a, float b)
+{
+       /* A film of F seconds at f FPS will be Ff frames;
+          Consider some delta FPS d, so if we run the same
+          film at (f + d) FPS it will last F(f + d) seconds.
+
+          Hence the difference in length over the length of the film will
+          be F(f + d) - Ff frames
+           = Ff + Fd - Ff frames
+           = Fd frames
+           = Fd/f seconds
+ 
+          So if we accept a difference of 1 frame, ie 1/f seconds, we can
+          say that
+
+          1/f = Fd/f
+       ie 1 = Fd
+       ie d = 1/F
+ 
+          So for a 3hr film, ie F = 3 * 60 * 60 = 10800, the acceptable
+          FPS error is 1/F ~= 0.0001 ~= 10-e4
+       */
+
+       return (fabs (a - b) < 1e-4);
+}
+
+class FrameRateCandidate
 {
-       DCPFrameRate dfr;
+public:
+       FrameRateCandidate (float source_, int dcp_)
+               : source (source_)
+               , dcp (dcp_)
+       {}
 
-       dfr.run_fast = (fps != rint (fps));
-       dfr.frames_per_second = rint (fps);
-       dfr.skip = 1;
+       bool skip () const {
+               return !about_equal (source, dcp) && source > dcp;
+       }
+
+       bool repeat () const {
+               return !about_equal (source, dcp) && source < dcp;
+       }
+
+       float source;
+       int dcp;
+};
+
+/** @param fps Arbitrary source frames-per-second value */
+/** XXX: this could be slow-ish */
+DCPFrameRate::DCPFrameRate (float source_fps)
+{
+       list<int> const allowed_dcp_frame_rates = Config::instance()->allowed_dcp_frame_rates ();
+
+       /* Work out what rates we could manage, including those achieved by using skip / repeat. */
+       list<FrameRateCandidate> candidates;
+
+       /* Start with the ones without skip / repeat so they will get matched in preference to skipped/repeated ones */
+       for (list<int>::const_iterator i = allowed_dcp_frame_rates.begin(); i != allowed_dcp_frame_rates.end(); ++i) {
+               candidates.push_back (FrameRateCandidate (*i, *i));
+       }
+
+       /* Then the skip/repeat ones */
+       for (list<int>::const_iterator i = allowed_dcp_frame_rates.begin(); i != allowed_dcp_frame_rates.end(); ++i) {
+               candidates.push_back (FrameRateCandidate (float (*i) / 2, *i));
+               candidates.push_back (FrameRateCandidate (float (*i) * 2, *i));
+       }
+
+       /* Pick the best one, bailing early if we hit an exact match */
+       float error = numeric_limits<float>::max ();
+       boost::optional<FrameRateCandidate> best;
+       list<FrameRateCandidate>::iterator i = candidates.begin();
+       while (i != candidates.end()) {
+               
+               if (about_equal (i->source, source_fps)) {
+                       best = *i;
+                       break;
+               }
+
+               float const e = fabs (i->source - source_fps);
+               if (e < error) {
+                       error = e;
+                       best = *i;
+               }
+
+               ++i;
+       }
 
-       /* XXX: somewhat arbitrary */
-       if (fps == 50) {
-               dfr.frames_per_second = 25;
-               dfr.skip = 2;
+       if (!best) {
+               throw EncodeError ("cannot find a suitable DCP frame rate for this source");
        }
 
-       return dfr;
+       frames_per_second = best->dcp;
+       skip = best->skip ();
+       repeat = best->repeat ();
+       change_speed = !about_equal (source_fps * factor(), frames_per_second);
 }
 
 /** @param An arbitrary sampling rate.