Why chunk direction are not constant ?

Cecile_Radix · January 19, 2018, 5:11pm

We have created a Live application with following properties :

<LiveStreamPacketizer>
  <!-- Properties defined here will override any properties defined in conf/LiveStreamPacketizers.xml for any LiveStreamPacketizers loaded by this applications -->    

<Properties>

	<Property>
   		<Name>cupertinoChunkDurationTarget</Name>
		<Value>8000</Value>
		<Type>Integer</Type>
	</Property>
	<Property>
		<Name>cupertinoPlaylistChunkCount</Name>
		<Value>10</Value>
		<Type>Integer</Type>
	</Property>
</Properties>

</LiveStreamPacketizer>

Associated transcoder template is:

<?xml version="1.0" encoding="UTF-8"?>
<Root>
<Transcode>
<Description></Description>
<Decode>
<Video>
<Implementation>default</Implementation>
<Deinterlace>false</Deinterlace>
</Video>
</Decode>
<Encodes>
<Encode>
<Name>320x180</Name>
<Enable>true</Enable>
<Description>320x180</Description>
<StreamName>mp4:${SourceStreamName}_320x180</StreamName>
<Video>
<Codec>H.264</Codec>
<Implementation>default</Implementation>
<GPUID>-1</GPUID>
<Profile>baseline</Profile>
<Bitrate>226000</Bitrate>
<KeyFrameInterval>
<FollowSource>false</FollowSource>
<Interval>12</Interval>
</KeyFrameInterval>
<FrameSize>
<FitMode>crop</FitMode>
<Width>320</Width>
<Height>180</Height>
<Crop>0,0,0,0</Crop>
<SourceRectangle></SourceRectangle>
</FrameSize>
</Video>
<Audio>
<Codec>AAC</Codec>
<Bitrate>128000</Bitrate>
</Audio>
</Encode>
<Encode>
<Name>640x360</Name>
<Enable>true</Enable>
<Description>640x360</Description>
<StreamName>mp4:${SourceStreamName}_640x360</StreamName>
<Video>
<Codec>H.264</Codec>
<Implementation>default</Implementation>
<GPUID>-1</GPUID>
<Profile>main</Profile>
<Bitrate>1200000</Bitrate>
<KeyFrameInterval>
<FollowSource>false</FollowSource>
<Interval>24</Interval>
</KeyFrameInterval>
<FrameSize>
<FitMode>crop</FitMode>
<Width>640</Width>
<Height>360</Height>
<Crop>0,0,0,0</Crop>
<SourceRectangle></SourceRectangle>
</FrameSize>
<Parameters>
<Parameter>
<Name>mainconcept.bit_rate_mode</Name>
<Value>0</Value>
<Type>Long</Type>
</Parameter>
<Parameter>
<Name>mainconcept.bit_rate</Name>
<Value>1000000</Value>
<Type>Long</Type>
</Parameter>
<Parameter>
<Name>mainconcept.bit_rate_buffer_size</Name>
<Value>40000</Value>
<Type>Long</Type>
</Parameter>
</Parameters>
</Video>
<Audio>
<Codec>AAC</Codec>
<Bitrate>128000</Bitrate>
</Audio>
</Encode>
<Encode>
<Name>1024x576</Name>
<Enable>true</Enable>
<Description>1024x576</Description>
<StreamName>mp4:${SourceStreamName}_1024x576</StreamName>
<Video>
<Codec>H.264</Codec>
<Implementation>default</Implementation>
<GPUID>-1</GPUID>
<Profile>main</Profile>
<Bitrate>2100000</Bitrate>
<KeyFrameInterval>
<FollowSource>false</FollowSource>
<Interval>32</Interval>
</KeyFrameInterval>
<FrameSize>
<FitMode>crop</FitMode>
<Width>1024</Width>
<Height>576</Height>
<Crop>0,0,0,0</Crop>
<SourceRectangle></SourceRectangle>
</FrameSize>
</Video>
<Audio>
<Codec>AAC</Codec>
<Bitrate>128000</Bitrate>
</Audio>
</Encode>
<Encode>
<Name>416x234</Name>
<Enable>true</Enable>
<Description>416x234</Description>
<StreamName>mp4:${SourceStreamName}_416x234</StreamName>
<Video>
<Codec>H.264</Codec>
<Implementation>default</Implementation>
<GPUID>-1</GPUID>
<Profile>baseline</Profile>
<Bitrate>450000</Bitrate>
<KeyFrameInterval>
<FollowSource>false</FollowSource>
<Interval>12</Interval>
</KeyFrameInterval>
<FrameSize>
<FitMode>crop</FitMode>
<Width>416</Width>
<Height>234</Height>
<Crop>0,0,0,0</Crop>
<SourceRectangle></SourceRectangle>
</FrameSize>
</Video>
<Audio>
<Codec>AAC</Codec>
<Bitrate>128000</Bitrate>
</Audio>
</Encode>
<Encode>
<Name>240x135</Name>
<Enable>true</Enable>
<Description>240x135</Description>
<StreamName>mp4:${SourceStreamName}_240x135</StreamName>
<Video>
<Codec>H.264</Codec>
<Implementation>default</Implementation>
<GPUID>-1</GPUID>
<Profile>baseline</Profile>
<Bitrate>120000</Bitrate>
<KeyFrameInterval>
<FollowSource>false</FollowSource>
<Interval>12</Interval>
</KeyFrameInterval>
<FrameSize>
<FitMode>crop</FitMode>
<Width>240</Width>
<Height>135</Height>
<Crop>0,0,0,0</Crop>
<SourceRectangle></SourceRectangle>
</FrameSize>
</Video>
<Audio>
<Codec>AAC</Codec>
<Bitrate>128000</Bitrate>
</Audio>
</Encode>
<Encode>
<Name>1280x720</Name>
<Enable>true</Enable>
<Description>1280x720</Description>
<StreamName>mp4:${SourceStreamName}_1280x720</StreamName>
<Video>
<Codec>H.264</Codec>
<Implementation>default</Implementation>
<GPUID>-1</GPUID>
<Profile>main</Profile>
<Bitrate>3000000</Bitrate>
<KeyFrameInterval>
<FollowSource>true</FollowSource>
<Interval>0</Interval>
</KeyFrameInterval>
<FrameSize>
<FitMode>match-source</FitMode>
<Width>0</Width>
<Height>0</Height>
<Crop>0,0,0,0</Crop>
<SourceRectangle></SourceRectangle>
</FrameSize>
</Video>
<Audio>
<Codec>AAC</Codec>
<Bitrate>128000</Bitrate>
</Audio>
</Encode>
<Encode>
<Name>480x270</Name>
<Enable>true</Enable>
<Description>480x270</Description>
<StreamName>mp4:${SourceStreamName}_480x270</StreamName>
<Video>
<Codec>H.264</Codec>
<Implementation>default</Implementation>
<GPUID>-1</GPUID>
<Profile>baseline</Profile>
<Bitrate>680000</Bitrate>
<KeyFrameInterval>
<FollowSource>false</FollowSource>
<Interval>24</Interval>
</KeyFrameInterval>
<FrameSize>
<FitMode>crop</FitMode>
<Width>480</Width>
<Height>270</Height>
<Crop>0,0,0,0</Crop>
<SourceRectangle></SourceRectangle>
</FrameSize>
</Video>
<Audio>
<Codec>AAC</Codec>
<Bitrate>128000</Bitrate>
</Audio>
</Encode>
</Encodes>
</Transcode>
</Root>

So you can see that all key frames internal are multiples of 8.

But as result, we have inconstant chunk duration :

#EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:10
#EXT-X-MEDIA-SEQUENCE:1
#EXTINF:8.0,
https://XXXX/media_w955918613_b184000_slfr_1.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a 

#EXTINF:8.75,
https://XXXXXXX/media_w955918613_b184000_slfr_2.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:8.406,
https://XXXXXXX/media_w955918613_b184000_slfr_3.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:7.5,
https://XXXXXXX/media_w955918613_b184000_slfr_4.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:7.344,
https://XXXXXXX/media_w955918613_b184000_slfr_5.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:8.906,
https://XXXXXXX/media_w955918613_b184000_slfr_6.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:7.344,
https://XXXXXXX/media_w955918613_b184000_slfr_7.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:7.844,
https://XXXXXXX/media_w955918613_b184000_slfr_8.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:9.375,
https://XXXXXXX/media_w955918613_b184000_slfr_9.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a
#EXTINF:7.5,
https://XXXXXXX/media_w955918613_b184000_slfr_10.ts?bearer=LTE&sid=f389f231-f5ca-484f-a5c3-36a83be0201a

We don’t understand why we have chunks of multiple durations.

We try to set input stream frame rate at 32 fps but it does not help.

system · January 19, 2018, 8:51pm

You need to have your live encoder generate a stable keyframe distance which is also known as a Group of Pictures or GOP. Once you have your keyframe consistent from your encoder please change the chunk duration to match that value.

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Why chunk direction are not constant ?

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