CMAF LL-HLS在Safari/QuickTime高延迟问题排查及技术咨询

现象描述 #

• 通过Wowza搭建的CMAF LL-HLS播放链接，在HTML5播放器及Chrome的HLS播放器中，延迟可稳定控制在4-5秒
• 但在Mac端Safari 15.1版本及QuickTime中，延迟高达12-18秒，远不符合低延迟预期

核心疑问 #

• 是Safari和QuickTime本身不支持CMAF LL-HLS的低延迟特性？
• 还是生成的m3u8文件存在错误，导致低延迟未生效？

生成的m3u8文件内容 #

#EXTM3U
#EXT-X-VERSION:6
#EXT-X-SERVER-CONTROL:CAN-BLOCK-RELOAD=YES,PART-HOLD-BACK=3.009,CAN-SKIP-UNTIL=42.0
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-TARGETDURATION:7
#EXT-X-MEDIA-SEQUENCE:21
#EXT-X-PART-INF:PART-TARGET=1.0
#EXT-X-RENDITION-REPORT:URI="chunklist_b1000000_vo_sfm4s.m3u8",LAST-MSN=26,LAST-PART=0
#EXT-X-RENDITION-REPORT:URI="chunklist_b600000_vo_sfm4s.m3u8",LAST-MSN=26,LAST-PART=0
#EXT-X-RENDITION-REPORT:URI="chunklist_b96000_ao_sfm4s_sleng_t64RW5nbGlzaA==.m3u8",LAST-MSN=26,LAST-PART=0
#EXT-X-MAP:URI="header-u9f4vz01t_b800000_vo_sfm4s_m3u8.cmfv"
#EXT-X-PROGRAM-DATE-TIME:2024-08-09T06:49:13.781+00:00
#EXTINF:6.0,
media-u9f4vz01t_b800000_vo_sfm4s_21_m3u8.cmfv
#EXT-X-PROGRAM-DATE-TIME:2024-08-09T06:49:19.802+00:00
#EXTINF:6.0,
media-u9f4vz01t_b800000_vo_sfm4s_22_m3u8.cmfv
#EXT-X-PROGRAM-DATE-TIME:2024-08-09T06:49:25.759+00:00
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_23.0_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_23.1_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_23.2_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_23.3_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_23.4_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_23.5_m3u8.cmfv",INDEPENDENT=YES
#EXTINF:6.0,
media-u9f4vz01t_b800000_vo_sfm4s_23_m3u8.cmfv
#EXT-X-PROGRAM-DATE-TIME:2024-08-09T06:49:31.771+00:00
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_24.0_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_24.1_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_24.2_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_24.3_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_24.4_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_24.5_m3u8.cmfv",INDEPENDENT=YES
#EXTINF:6.0,
media-u9f4vz01t_b800000_vo_sfm4s_24_m3u8.cmfv
#EXT-X-PROGRAM-DATE-TIME:2024-08-09T06:49:37.729+00:00
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_25.0_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_25.1_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_25.2_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_25.3_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_25.4_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_25.5_m3u8.cmfv",INDEPENDENT=YES
#EXTINF:6.0,
media-u9f4vz01t_b800000_vo_sfm4s_25_m3u8.cmfv
#EXT-X-PROGRAM-DATE-TIME:2024-08-09T06:49:43.747+00:00
#EXT-X-PART:DURATION=1.0,URI="media-u9f4vz01t_b800000_vo_sfm4s_26.0_m3u8.cmfv",INDEPENDENT=YES
#EXT-X-PRELOAD-HINT:TYPE=PART,URI="media-u9f4vz01t_b800000_vo_sfm4s_26.1_m3u8.cmfv"

求助需求 #

1. 若上述m3u8文件存在错误，请指出问题原因
2. 推荐可测试Wowza生成的CMAF LL-HLS链接的iOS原生应用
3. 若Safari和QuickTime本身不支持CMAF LL-HLS低延迟，请告知iOS播放器开发时需配置的选项或需完成的任务

内容的提问来源于stack exchange，提问作者Jay