Get empty close caption sometimes

Wowza Streaming Engine
1

here is my smil file

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<smil title="">
        <head/>
        <body>
                <switch>
                <video height="480" src="2588_720x480" systemLanguage="def" video-bitrate="800000" width="720">
                        <param name="videoBitrate" value="800000" valuetype="data"/>
                        <param name="audioBitrate" value="128000" valuetype="data"/>
                </video>
                <video height="540" src="2588_960x540" systemLanguage="def" video-bitrate="1000000" width="960">
                        <param name="videoBitrate" value="1000000" valuetype="data"/>
                        <param name="audioBitrate" value="128000" valuetype="data"/>
                </video>
                <video height="720" src="2588_1280x720" systemLanguage="def" video-bitrate="2000000" width="1280">
                        <param name="videoBitrate" value="2000000" valuetype="data"/>
                        <param name="audioBitrate" value="128000" valuetype="data"/>
                </video>
                <video height="1080" src="2588_1920x1080" systemLanguage="def" video-bitrate="4000000" width="1920">
                        <param name="videoBitrate" value="4000000" valuetype="data"/>
                        <param name="audioBitrate" value="128000" valuetype="data"/>
                </video>
        <textstream src="ttmlsub/2588.ttml" system-language="chi,jpn,deu,kor,fre,eng,ita,spa,abk">
                <param name="isWowzaCaptionStream" value="true"/>
                <param name="wowzaCaptionIngestType" value="onTextData"/>
            </textstream>
        </switch>
        </body>
</smil>

my problem is:

  1. Usually, it could generate right text stream, but sometimes i may have chance get empty text stream

correct text
WEBVTT
X-TIMESTAMP-MAP=MPEGTS:0,LOCAL:00:00:00.000

00:20:55.900 --> 00:21:02.533
是啊 我完成艱難的事
你們覺得可惜嗎

00:21:05.667 --> 00:21:07.433
也沒什麼

00:21:07.433 --> 00:21:08.800
反正就是談成了

00:21:09.533 --> 00:21:11.833
我可以打給ViKings了吧

00:21:11.833 --> 00:21:14.200
還有人反對的話

00:21:14.200 --> 00:21:16.700
趁我出去之前叫我的名字

00:21:16.700 --> 00:21:18.633
我…

00:21:18.633 --> 00:21:20.933
會慢慢地走出去

00:21:36.333 --> 00:21:37.633
這是怎樣啦

00:21:38.000 --> 00:21:39.433
他得到姜斗基了嗎

00:21:40.467 --> 00:21:41.433
怎麼回事

00:21:43.533 --> 00:21:45.000
這像話嗎

00:22:03.367 --> 00:22:04.500
是真的嗎

00:22:05.933 --> 00:22:07.433
您會同意吧

00:22:22.300 --> 00:22:23.600
去打包行李吧

00:22:34.767 --> 00:22:35.967
趕快

00:22:36.600 --> 00:22:38.500
還有把這個也帶走

00:22:45.067 --> 00:22:50.000
修車的部分 我是自己出錢

00:22:53.567 --> 00:22:54.567
喂

00:22:56.033 --> 00:22:57.433
別鬧了

00:23:01.800 --> 00:23:04.433
你不要用這種方式
對ViKings的團長

00:23:04.433 --> 00:23:07.367
我和金冠植互換嗎

00:23:07.367 --> 00:23:09.200
你覺得粉絲會善罷甘休嗎

00:23:09.900 --> 00:23:13.067
能在Dreams史上留下退休背號的人
只有我

00:23:13.067 --> 00:23:15.400
你想看球團巴士著火嗎

00:23:16.367 --> 00:23:18.733
為什麼要放火

00:23:18.733 --> 00:23:22.433
大家一聽到姜斗基選手要來
都會很開心

00:23:27.733 --> 00:23:29.000
姜斗基嗎

00:23:30.333 --> 00:23:33.900
是他那種選手要留下退休背號

00:23:33.900 --> 00:23:36.133
會打棒球

00:23:36.133 --> 00:23:38.767
受同伴們尊敬的選手

00:23:38.767 --> 00:23:43.600
當然林東奎選手明知道要轉走

00:23:43.600 --> 00:23:46.100
卻還捐裝備給球隊

00:23:46.100 --> 00:23:50.467
又主動支付聚餐的費用
這是非常美麗的善舉

00:23:50.467 --> 00:23:54.167
托你的福 我們球隊也沒發現
我們關係不好的事

00:23:54.167 --> 00:23:56.700
到最後都表現得很好

00:23:57.667 --> 00:23:58.633
托林東奎選手的福

00:23:58.633 --> 00:24:01.633
國家代表第1先發球員要來我們隊

00:24:05.200 --> 00:24:06.633
為什麼是姜斗基…

00:24:18.933 --> 00:24:20.133
你

00:24:22.600 --> 00:24:27.067
以為我在這裡打11年球
會像這樣落寞地結束嗎

00:24:27.067 --> 00:24:30.100
趕走你這種傢伙會很難嗎

00:24:31.467 --> 00:24:34.733
從現在開始
你在這裡無法移動半步

00:24:35.567 --> 00:24:37.933
喂 林東奎

00:24:37.933 --> 00:24:39.300
你說什麼 臭小子

00:24:54.500 --> 00:24:55.767
走吧

empty:
WEBVTT
X-TIMESTAMP-MAP=MPEGTS:0,LOCAL:00:00:00.000

and I have no idea what caused it to happen? performance issue?

second , the chunklist duration are always about 250 seconds, is that tunable?

#EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:251
#EXT-X-MEDIA-SEQUENCE:0
#EXTINF:250,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_0.webvtt
#EXTINF:251,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_25.webvtt
#EXTINF:250,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_50.webvtt
#EXTINF:250,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_75.webvtt
#EXTINF:250,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_100.webvtt
#EXTINF:251,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_125.webvtt
#EXTINF:250,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_150.webvtt
#EXTINF:94,
subtitlechunk_lchi_w1750196936_b928000_sldef_cfdHRtbHN1Yi80NzU4OC50dG1s_175.webvtt
#EXT-X-ENDLIST

2

Hello @Trick_Chen, just so you know in case you didn’t see it in the community articles, if you’d like Wowza to officially review your smil file you’ll need to submit a support ticket. The forums are for resource/docs guidance, but not an official source of Wowza technical support. A ticket is the only way we can accurately troubleshoot and provide a quality solution.

You can submit it here and an engineer will work with you to identify the issues with the captions.

Here’s doc to perhaps help you in the meantime (if you didn’t see it yet) and has some directions for WebVTT:

Configure WebVTT captions for Wowza Streaming Engine iOS streams

https://www.wowza.com/docs/how-to-stream-webvtt-subtitles-to-ios-for-closed-captioning:

3

ok !
Thank you! :grinning: :grinning: :grinning: :grinning: