Is there a time limit on length of downloads?

[RS]

This is probably a ffmpeg problem, but I mention it here in case it is a 
problem with what get_iplayer is passing to ffmpeg.  I have downloaded 
the Red Button coverage of the cross-country day at Badminton (p065zgf4) 
using hvfxsd3 from Akamai.  The resultant .mp4 file is 4.6GByte and the 
duration is 5h 56min.  The .mp4 file plays fine in VLC, and if I seek to 
a different part of the file it does so within 500ms.

During the conversion by ffmpeg I got a large number of error messages like

[mpegts @ 0x56028af28400] Invalid timestamps stream=1, pts=160090200, 
dts=160092000, size=7261
[mp4 @ 0x56028af58360] Invalid DTS: 159190200 PTS: 159188400 in output 
stream 0:0, replacing by guess
[mp4 @ 0x56028af58360] Invalid DTS: 159192000 PTS: 159190200 in output 
stream 0:0, replacing by guess
[mpegts @ 0x56028af28400] Invalid timestamps stream=1, pts=160093800, 
dts=160095600, size=1747
[mpegts @ 0x56028af28400] Invalid timestamps stream=1, pts=160095600, 
dts=160097400, size=7676
[mp4 @ 0x56028af58360] Invalid DTS: 159195600 PTS: 159193800 in output 
stream 0:0, replacing by guess

Is there a limit on the length of recording get_iplayer can handle, or 
is it a ffmpeg problem?

We were recently discussing the withdrawal of HLS modes.  When the HLShd 
mode existed it was never made available for Red Button channels.  What 
I could not remember was whether other HD modes were produced.  In this 
case all the HVF modes including HVFhd were present, even though the Red 
Button is usually a SD channel.  get_iplayer's estimate of hvfhd file 
size was 15290MByte!