avformat/movenc: Add support for writing 'gama' atom to QuickTime .mov files.

As this is depricated it should not be on by default, it is only
supported for MOV containers, depends on avpriv_get_gamma_from_trc()

Enable by:

-movflags +write_gama

This will use the color_trc to supply a gamma value, if desired an
explicit value may be supplied using the -mov_gamma option supplying
a suitable floating point value, values <=1e-6 will not be written.
Signed-off-by: Kevin Wheatley <kevin.j.wheatley@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/movenc.c

@@ -40,10 +40,12 @@
 #include "libavutil/avstring.h"
 #include "libavutil/intfloat.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/libm.h"
 #include "libavutil/opt.h"
 #include "libavutil/dict.h"
 #include "libavutil/pixdesc.h"
 #include "libavutil/timecode.h"
+#include "libavutil/color_utils.h"
 #include "hevc.h"
 #include "rtpenc.h"
 #include "mov_chan.h"
@@ -65,6 +67,7 @@ static const AVOption options[] = {
     { "frag_discont", "Signal that the next fragment is discontinuous from earlier ones", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_FRAG_DISCONT}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     { "delay_moov", "Delay writing the initial moov until the first fragment is cut, or until the first fragment flush", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_DELAY_MOOV}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     { "write_colr", "Write colr atom (Experimental, may be renamed or changed, do not use from scripts)", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_WRITE_COLR}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
+    { "write_gama", "Write deprecated gama atom", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_WRITE_GAMA}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     FF_RTP_FLAG_OPTS(MOVMuxContext, rtp_flags),
     { "skip_iods", "Skip writing iods atom.", offsetof(MOVMuxContext, iods_skip), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
     { "iods_audio_profile", "iods audio profile atom.", offsetof(MOVMuxContext, iods_audio_profile), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 255, AV_OPT_FLAG_ENCODING_PARAM},
@@ -77,6 +80,7 @@ static const AVOption options[] = {
     { "brand",    "Override major brand", offsetof(MOVMuxContext, major_brand),   AV_OPT_TYPE_STRING, {.str = NULL}, .flags = AV_OPT_FLAG_ENCODING_PARAM },
     { "use_editlist", "use edit list", offsetof(MOVMuxContext, use_editlist), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 1, AV_OPT_FLAG_ENCODING_PARAM},
     { "fragment_index", "Fragment number of the next fragment", offsetof(MOVMuxContext, fragments), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM},
+    { "mov_gamma", "gamma value for gama atom", offsetof(MOVMuxContext, gamma), AV_OPT_TYPE_FLOAT, {.dbl = 0.0 }, 0.0, 10, AV_OPT_FLAG_ENCODING_PARAM},
     { NULL },
 };
 
@@ -1519,6 +1523,31 @@ static int mov_write_pasp_tag(AVIOContext *pb, MOVTrack *track)
     return 16;
 }
 
+static int mov_write_gama_tag(AVIOContext *pb, MOVTrack *track, double gamma)
+{
+    uint32_t gama = 0;
+    if (gamma <= 0.0)
+    {
+        gamma = avpriv_get_gamma_from_trc(track->enc->color_trc);
+    }
+    av_log(pb, AV_LOG_DEBUG, "gamma value %g\n", gamma);
+
+    if (gamma > 1e-6) {
+        gama = (uint32_t)lrint((double)(1<<16) * gamma);
+        av_log(pb, AV_LOG_DEBUG, "writing gama value %d\n", gama);
+
+        av_assert0(track->mode == MODE_MOV);
+        avio_wb32(pb, 12);
+        ffio_wfourcc(pb, "gama");
+        avio_wb32(pb, gama);
+        return 12;
+    }
+    else {
+        av_log(pb, AV_LOG_WARNING, "gamma value unknown, unable to write gama atom\n");
+    }
+    return 0;
+}
+
 static int mov_write_colr_tag(AVIOContext *pb, MOVTrack *track)
 {
     // Ref (MOV): https://developer.apple.com/library/mac/technotes/tn2162/_index.html#//apple_ref/doc/uid/DTS40013070-CH1-TNTAG9
@@ -1700,6 +1729,12 @@ static int mov_write_video_tag(AVIOContext *pb, MOVMuxContext *mov, MOVTrack *tr
         if (track->enc->field_order != AV_FIELD_UNKNOWN)
             mov_write_fiel_tag(pb, track);
 
+    if (mov->flags & FF_MOV_FLAG_WRITE_GAMA) {
+        if (track->mode == MODE_MOV)
+            mov_write_gama_tag(pb, track, mov->gamma);
+        else
+            av_log(mov->fc, AV_LOG_WARNING, "Not writing 'gama' atom. Format is not MOV.\n");
+    }
     if (mov->flags & FF_MOV_FLAG_WRITE_COLR) {
         if (track->mode == MODE_MOV || track->mode == MODE_MP4)
             mov_write_colr_tag(pb, track);

libavformat/movenc.h

@@ -185,6 +185,7 @@ typedef struct MOVMuxContext {
     AVFormatContext *fc;
 
     int use_editlist;
+    float gamma;
 } MOVMuxContext;
 
 #define FF_MOV_FLAG_RTP_HINT              (1 <<  0)
@@ -202,6 +203,7 @@ typedef struct MOVMuxContext {
 #define FF_MOV_FLAG_FRAG_DISCONT          (1 << 12)
 #define FF_MOV_FLAG_DELAY_MOOV            (1 << 13)
 #define FF_MOV_FLAG_WRITE_COLR            (1 << 14)
+#define FF_MOV_FLAG_WRITE_GAMA            (1 << 15)
 
 int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt);