[NUT-devel] [PATCH 2/2] nut: per frame side and meta data support

[Michael Niedermayer]

This variant is simpler and has less overhead than the previous
It is not compatible with existing demuxers though, the reasoning here
is that as side data is essential for presentation of a stream demuxer support
is neccessary anyway.

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
---
 docs/nut.txt |   98 ++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 74 insertions(+), 24 deletions(-)

diff --git a/docs/nut.txt b/docs/nut.txt
index 44198c1..e414904 100644
--- a/docs/nut.txt
+++ b/docs/nut.txt
@@ -353,6 +353,46 @@ frame:
     }
     data
 
+data:
+    if (frame_flags&FLAG_SM_DATA) {
+        side_data
+        meta_data
+    }
+    frame_data
+
+side_data
+    sm_data
+
+meta_data
+    sm_data
+
+sm_data:
+    count                               v
+    for(i=0; i<count; i++){
+        name                            vb
+        value                           s
+        if (value==-1){
+            type= "UTF-8"
+            value                       vb
+        }else if (value==-2){
+            type                        vb
+            value                       vb
+        }else if (value==-3){
+            type= "s"
+            value                       s
+        }else if (value==-4){
+            type= "t"
+            value                       t
+        }else if (value<-4){
+            type= "r"
+            value.den= -value-4
+            value.num                   s
+        }else{
+            type= "v"
+        }
+    }
+
+
 index:
     max_pts                             t
     syncpoints                          v
@@ -401,30 +441,7 @@ info_packet:
                                            until 2006-11-04.)
     chapter_start                       t
     chapter_len                         v
-    count                               v
-    for(i=0; i<count; i++){
-        name                            vb
-        value                           s
-        if (value==-1){
-            type= "UTF-8"
-            value                       vb
-        }else if (value==-2){
-            type                        vb
-            value                       vb
-        }else if (value==-3){
-            type= "s"
-            value                       s
-        }else if (value==-4){
-            type= "t"
-            value                       t
-        }else if (value<-4){
-            type= "r"
-            value.den= -value-4
-            value.num                   s
-        }else{
-            type= "v"
-        }
-    }
+    meta_data
     reserved_bytes
 
 syncpoint:
@@ -651,6 +668,8 @@ flags[frame_code], frame_flags (v)
                            otherwise data_size_msb is 0.
        6  FLAG_CHECKSUM    If set, the frame header contains a checksum.
        7  FLAG_RESERVED    If set, reserved_count is coded in the frame header.
+       8  FLAG_SM_DATA     If set, side/meta data is stored with the frame data.
+                           This flag MUST NOT be set in version < 4
       10  FLAG_HEADER_IDX  If set, header_idx is coded in the frame header.
       11  FLAG_MATCH_TIME  If set, match_time_delta is coded in the frame
                            header
@@ -700,6 +719,37 @@ pts_delta[frame_code] (s)
 reserved_count[frame_code] (v)
     MUST be <256.
 
+sm_data / side_data / meta_data
+    This data structure is used both in frames for per frame side and metadata
+    as well as info tags for metadata covering the whole file, a stream
+    chapter or other.
+    Metadata is data that is about the actual data and generally not essential
+    for correct presentation
+    Sidedata is semantically part of the data and essential for its correct
+    presentation. The same syntax is used by both for simplicity.
+    Types of per frame side data:
+    "Channels", "ChannelLayout", "SampleRate", "Width", "Height"
+        This frame changes the number of channels, the channel layout, ... to
+        the given value (ChannelLayout vb, else v)
+        If used in any frame of a stream then every keyframe of the stream
+        SHOULD carry such sidedata to allow seeking.
+    "Extradata", "Palette"
+        This frame changes the codec_specific_data or palette to the given
+        value (vb)
+        If used in any frame of a stream then every keyframe of the stream
+        SHOULD carry such sidedata to allow seeking.
+    "CodecSpecificSide<num>"
+        Codec specific side data, equivalent to matroskas BlockAdditional (vb)
+        the "<num>" should be replaced by a number identifying the type of
+        side data, it is equivalent/equal to BlockAddId in matroska.
+    "SkipStart", "SkipEnd"
+        The decoder should skip/drop the specified number of samples at the
+        start/end of this frame (v)
+    "UserData<identifer here>"
+        User specific side data, the "<identifer here>" should be replaced
+        by a globally unique identifer of the project that
+        uses/creates/understands the side data. For example "UserDataFFmpeg"
+
 data_size
     data_size = data_size_lsb + data_size_msb * data_size_mul ;
     The size of the following frame, including a possible elision header.
-- 
1.7.9.5