[FFmpeg-devel] [PATCH 03/13] lavc/codec_desc: add a property for codecs that support field coding

[Anton Khirnov]

Multiple places currently use AVCodecContext.ticks_per_frame > 1 to
identify such codecs, which
* requires a codec context
* requires it to be open
---
 doc/APIchanges          |  3 +++
 libavcodec/codec_desc.c | 16 ++++++++++++----
 libavcodec/codec_desc.h |  6 ++++++
 libavcodec/version.h    |  2 +-
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index fd01def1b2..777485ce86 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,9 @@ The last version increases of all libraries were on 2023-02-09
 
 API changes, most recent first:
 
+2023-05-xx - xxxxxxxxxx - lavc 60.11.100 - codec_desc.h
+  Add AV_CODEC_PROP_FIELDS.
+
 2023-05-04 - xxxxxxxxxx - lavu 58.7.100 - frame.h
   Deprecate AVFrame.interlaced_frame, AVFrame.top_field_first, and
   AVFrame.key_frame.
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index d40977d6b3..49dddd1a49 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -38,14 +38,20 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .type      = AVMEDIA_TYPE_VIDEO,
         .name      = "mpeg1video",
         .long_name = NULL_IF_CONFIG_SMALL("MPEG-1 video"),
-        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_REORDER,
+        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_REORDER |
+                     // FIXME this is strigly speaking not true, as MPEG-1 does
+                     // not allow field coding, but our mpeg12 code (decoder and
+                     // parser) can sometimes change codec id at runtime, so
+                     // this is safer
+                     AV_CODEC_PROP_FIELDS,
     },
     {
         .id        = AV_CODEC_ID_MPEG2VIDEO,
         .type      = AVMEDIA_TYPE_VIDEO,
         .name      = "mpeg2video",
         .long_name = NULL_IF_CONFIG_SMALL("MPEG-2 video"),
-        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_REORDER,
+        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_REORDER |
+                     AV_CODEC_PROP_FIELDS,
         .profiles  = NULL_IF_CONFIG_SMALL(ff_mpeg2_video_profiles),
     },
     {
@@ -225,7 +231,8 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .type      = AVMEDIA_TYPE_VIDEO,
         .name      = "h264",
         .long_name = NULL_IF_CONFIG_SMALL("H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10"),
-        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_LOSSLESS | AV_CODEC_PROP_REORDER,
+        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_LOSSLESS |
+                     AV_CODEC_PROP_REORDER | AV_CODEC_PROP_FIELDS,
         .profiles  = NULL_IF_CONFIG_SMALL(ff_h264_profiles),
     },
     {
@@ -529,7 +536,8 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .type      = AVMEDIA_TYPE_VIDEO,
         .name      = "vc1",
         .long_name = NULL_IF_CONFIG_SMALL("SMPTE VC-1"),
-        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_REORDER,
+        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_REORDER |
+                     AV_CODEC_PROP_FIELDS,
         .profiles  = NULL_IF_CONFIG_SMALL(ff_vc1_profiles),
     },
     {
diff --git a/libavcodec/codec_desc.h b/libavcodec/codec_desc.h
index 126b52df47..dd4491112b 100644
--- a/libavcodec/codec_desc.h
+++ b/libavcodec/codec_desc.h
@@ -90,6 +90,12 @@ typedef struct AVCodecDescriptor {
  * equal.
  */
 #define AV_CODEC_PROP_REORDER       (1 << 3)
+
+/**
+ * Video codec supports separate coding of fields in interlaced frames.
+ */
+#define AV_CODEC_PROP_FIELDS        (1 << 4)
+
 /**
  * Subtitle codec is bitmap based
  * Decoded AVSubtitle data can be read from the AVSubtitleRect->pict field.
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 80e2ae630d..8b53586be1 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,7 +29,7 @@
 
 #include "version_major.h"
 
-#define LIBAVCODEC_VERSION_MINOR  10
+#define LIBAVCODEC_VERSION_MINOR  11
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
-- 
2.39.2