Merge pull request #4 from rbouqueau/scte35

scte35 documentation

docs/Howtos/scte35-markers.md

@@ -0,0 +1,92 @@
+# Overview
+
+We discuss here about the ability to deal with dynamic metadata such as SCTE-35 in GPAC Filters.
+The information is this page applies to other metadata such as ID3 markers (e.g. Nielsen), timecodes (TEMI, QT), or virtually any type of dynamic metadata.
+
+A special [dec_scte35 filter](dec_scte35) allows to segment SCTE-35 content for 23001-18 CMAF Event Track creation.
+
+GPAC is able to:
+- inspect,
+- remux or transmux,
+- segment for DASH,
+- create 23001-18 ISOBMFF Event Track (with ```emib``` and ```emeb``` boxes),
+- edit these data to some extend.
+
+# Inspection
+
+The content can be inspect like any other content in GPAC.
+Packet-based inspection may allow to dump useful information for analysis and reprocessing.
+
+## GPAC inspect
+
+```
+gpac -i input inspect:analyze=full:deep:props
+```
+
+would output:
+
+```
+[...]
+<Packet number="970" PID="1" framing="complete" dts="1636452" cts="1640956" dur="1502" sap="0" ilace="0" corr="0" seek="0" bo="N/A" roll="0" crypt="0" vers="0" size="6799" lp="0" depo="0" depf="0" red="0" CRC32="0x17CDFEAC">
+ <SCTE35>
+  <scte35:SpliceInfoSection xmlns:scte35="urn:scte:scte35:2013:bin" sap_type="3" protocol_version="0" encrypted_packet="0" pts_adjustment="183000" tier="4095">
+   <scte35:SpliceInsert splice_event_id="4026531841" splice_event_cancel_indicator="False" out_of_network_indicator="True" program_splice_flag="True" duration_flag="False" splice_immediate_flag="False">
+    <scte35:SpliceTime pts_time="1813812"/>
+   </scte35:SpliceInsert>
+  </scte35:SpliceInfoSection>
+ </SCTE35>
+</Packet>
+[...]
+```
+
+## MP4Box -dxml
+
+```
+MP4Box -dxml scte35.mp4
+```
+
+scte35_dump.xml would contain for instance such descriptions for a sample:
+
+```
+[...]
+<NHNTSample number="94" DTS="41224943904144" dataLength="98" CTSOffset="0" isRAP="yes" mediaOffset="0" sourceByteOffset="13584" duration="48048" depends="24" >
+<EventMessageInstanceBox Size="98" Type="emib" Version="0" Flags="0" Specification="EventMessageTrack" Container="file" presentation_time_delta="122121" event_duration="239239" event_id="1" scheme_id_uri="urn:scte:scte35:2013:bin" value="" message_data="0xFC302500000000697800FFF01405F00000027FEFFE1D0AC9C1FE000DB07B0001010100001231F90A" >
+  <scte35:SpliceInfoSection xmlns:scte35="urn:scte:scte35:2013:bin" sap_type="3" protocol_version="0" encrypted_packet="0" pts_adjustment="27000" tier="4095">
+   <scte35:SpliceInsert splice_event_id="4026531842" splice_event_cancel_indicator="False" out_of_network_indicator="True" program_splice_flag="True" duration_flag="True" splice_immediate_flag="False">
+    <scte35:SpliceTime pts_time="487246273"/>
+    <scte35:BreakDuration duration="897147"/>
+   </scte35:SpliceInsert>
+  </scte35:SpliceInfoSection>
+</EventMessageInstanceBox>
+</NHNTSample>
+[...]
+```
+
+
+# Remux and transmux
+
+GPAC is able to remux any to any, including but not limited to:
+- TS to TS
+- MP4 (23001-18) to MP4 (23001-18)
+- TS to MP4 (23001-18)
+
+See specific instructions in the next section when segmenting for OTT packaging (MPEG-DASH, HLS).
+
+The command-line is trivial:
+
+```
+gpac -i input -o output
+```
+
+The format is selected automatically depending on the file extension (or can be forced with ```:ext=```).
+
+# Segmentation and 23001-18 ISOBMFF Event Track
+
+Adaptive streaming with DASH or HLS requires the content to be segmented. Simple segmentation (where content can be replicated over several segments without any change) works for all kind of streams.
+
+For SCTE-35 streams the [dec_scte35 filter](dec_scte35) must be explicitly loaded.
+Note that it can detect the segment duration from the [dasher](dasher) to create the right segmentation for you):
+
+```
+gpac -i input scte35dec -o output.mpd:segdur=2
+```

mkdocs.yml

@@ -89,6 +89,7 @@ nav:
     - GPAC and Python: Howtos/python.md
     - Simulating Real-Time sources: Howtos/realtime.md
     - ROUTE & ATSC3.0 services: Howtos/route.md
+    - SCTE-35, id3 markers, dynamic metadata: Howtos/scte35-markers.md
     - DASH & HLS:
       - Introduction: Howtos/dash/DASH-intro.md
       - MPEG-DASH basics: Howtos/dash/DASH-basics.md