Bug 226314

Summary: IOS Native player caption font size is varying from small to big as the video plays in full screen
Product: WebKit Reporter: Karthik Sundari <karthiksundari2315>
Component: MediaAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Minor CC: eric.carlson, jer.noble, peng.liu6, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: Safari 14   
Hardware: iPhone / iPad   
OS: iOS 14   
Attachments:
Description Flags
Test video showing varying captions none

Description Karthik Sundari 2021-05-26 20:44:24 PDT
Created attachment 429838 [details]
Test video showing varying captions

When an HLS(M3U8) live stream with closed captions is played on the native player in full-screen landscape mode. The captions seem to vary from small to big causing a bad UX experience. Please find a sample manifest. 

```
#EXTM3U
#EXT-X-VERSION:4
#EXT-X-MEDIA:TYPE=CLOSED-CAPTIONS,GROUP-ID="cc",NAME="English",LANGUAGE="en",DEFAULT=YES,AUTOSELECT=YES,INSTREAM-ID="CC1"
#EXT-X-STREAM-INF:BANDWIDTH=762800,CLOSED-CAPTIONS="cc",PROGRAM-ID=1,CODECS="avc1.4d401f,mp4a.40.5",RESOLUTION=512x288
EMP_CH4/track-muxed-repid-root_audio_video3-tc-.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=1018000,CLOSED-CAPTIONS="cc",PROGRAM-ID=1,CODECS="avc1.4d401f,mp4a.40.5",RESOLUTION=640x360
EMP_CH4/track-muxed-repid-root_audio_video2-tc-.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=2290400,CLOSED-CAPTIONS="cc",PROGRAM-ID=1,CODECS="avc1.4d401f,mp4a.40.5",RESOLUTION=1280x720
EMP_CH4/track-muxed-repid-root_audio_video1-tc-.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=3635600,CLOSED-CAPTIONS="cc",PROGRAM-ID=1,CODECS="avc1.640020,mp4a.40.5",RESOLUTION=1280x720
EMP_CH4/track-muxed-repid-root_audio_video0-tc-.m3u8

#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=352360,PROGRAM-ID=1,CODECS="avc1.640020",RESOLUTION=1280x720,URI="*****/track-iframe-repid-iframe0-tc-.m3u8"
```
Comment 1 Radar WebKit Bug Importer 2021-06-02 20:45:23 PDT
<rdar://problem/78796280>