lavc/encode: pass through frame durations to encoded packets

The generic code can only handle the no-delay case. Encoders with delay
need to be handled individually, which will be done in the following
commits.

3 files changed, 15 insertions, 4 deletions

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 9c246c455c..96ee88c4fa 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -2647,7 +2647,8 @@ int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame);
  *
  *                  frame->time_base should be set to the same value as
  *                  avctx->time_base. This is not required yet, but may be in
- *                  the future.
+ *                  the future. frame->duration will be ignored unless time_base
+ *                  is set.
  *
  *                  For audio:
  *                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
diff --git a/libavcodec/encode.c b/libavcodec/encode.c
index da910b1b60..76eb69bba8 100644
--- a/libavcodec/encode.c
+++ b/libavcodec/encode.c
@@ -230,10 +230,13 @@ static int encode_simple_internal(AVCodecContext *avctx, AVPacket *avpkt)
             if (avpkt->pts == AV_NOPTS_VALUE)
                 avpkt->pts = frame->pts;
 
-            if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
-                if (!avpkt->duration)
+            if (!avpkt->duration) {
+                if (frame->duration)
+                    avpkt->duration = frame->duration;
+                else if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
                     avpkt->duration = ff_samples_to_time_base(avctx,
                                                               frame->nb_samples);
+                }
             }
         }
 
@@ -424,6 +427,13 @@ FF_ENABLE_DEPRECATION_WARNINGS
             return ret;
     }
 
+    // only use the frame duration if the timebase is set;
+    // otherwise we cannot be sure that whatever value it has is in the right
+    // timebase, so we would produce an incorrect value, which is worse than
+    // none at all
+    if (!dst->time_base.num || !dst->time_base.den)
+        dst->duration = 0;
+
     return 0;
 }
 
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 12421666b9..d7d5fca6b2 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -30,7 +30,7 @@
 #include "version_major.h"
 
 #define LIBAVCODEC_VERSION_MINOR  42
-#define LIBAVCODEC_VERSION_MICRO 102
+#define LIBAVCODEC_VERSION_MICRO 103
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \