Tvheadend

I want to record an iptv channel that has subtitles.
If I record it with vlc directly from the source, the subtitles are correctly recorded.
When I record the same channel with tvheadend, the subtitles disappear.

The log says the subtitle was correctly recognized:

2017-05-26 22:23:57.650 dvr: "prueba" on "[007] #0 HD" recorder starting
2017-05-26 22:23:57.660 mpegts: [007] #0 HD in IPTV network - tuning on IPTV
2017-05-26 22:23:57.669 subscription: 0014: "DVR: prueba" subscribing on channel "[007] #0 HD", weight: 300, adapter: "IPTV", network: "IPTV network", mux: "[007] #0 HD", service: "[007] #0 HD", profile="pass"
2017-05-26 22:23:57.683 dvr: /media/PenDrive/prueba.ts from adapter: "IPTV", network: "IPTV network", mux: "[007] #0 HD", provider: "", service: "[007] #0 HD"
2017-05-26 22:23:57.690 dvr: # type lang resolution aspect ratio sample rate channels
2017-05-26 22:23:57.691 dvr: 1 H264 1920x1080 ?
2017-05-26 22:23:57.698 dvr: 2 TELETEXT
2017-05-26 22:23:57.698 dvr: 3 MPEG2AUDIO und ? ?
2017-05-26 22:23:57.700 dvr: 4 MPEG2AUDIO v.o ? ?
2017-05-26 22:23:57.700 dvr: 5 EAC3 und ? ?
2017-05-26 22:23:57.701 dvr: 6 EAC3 v.o ? ?
2017-05-26 22:23:57.701 dvr: 7 TEXTSUB und
2017-05-26 22:23:57.708 dvr: 8 TEXTSUB und
2017-05-26 22:23:57.709 dvr: 9 TEXTSUB srd
2017-05-26 22:23:57.709 dvr: 10 TEXTSUB cat
2017-05-26 22:23:57.709 dvr: 11 TEXTSUB baq
2017-05-26 22:24:00.003 subscription: 0014: "DVR: prueba" unsubscribing from "[007] #0 HD"
2017-05-26 22:24:00.011 dvr: "prueba" on "[007] #0 HD": End of program: Completed OK