I was planning make DVB USB be able to switch USB streaming parameters
dynamically. I mean [struct usb_data_stream_properties] parameters.
Currently it reserves USB streaming buffers when device is plugged. Own
buffer is reserved for each frontend, which means currently 1-3
streaming buffers depending on device.
Basically I see USB TS as a DVB USB device property - not property of
frontend. USB TS is interface between computer and USB-bridge and amount
of parallel USB TS or TS configurations depends on USB-bridge
capabilities. Sometimes used USB TS could be configured to fit better
used stream. Smaller buffers for the narrow radio stream and biggest
buffers for the wide DVB-S2 stream.
I was wondering how to resolve that situation? It is not very big
problem currently but I still want to make it better as there is surely
coming new devices that needs better control for the USB streaming
parameters. Currently there is mxl111sf driver which seems to offer 6
different streaming configurations but AFAIK only three is currently
used as there is 3 frontends and each one has own streaming parameters -
and buffers - even only one can be used at the time.
1. Configure streaming parameters (alloc buffers) every time when
streaming is started? IIRC that causes some problems lately for em28xx
as memory goes dis-coherent and buffers cannot allocated.
2. Allocate buffers (streaming configuration) for all needed device use
configurations at very beginning. Then add some logic to map streaming
config to frontend at runtime. That is quite near what mxl111sf does
currently.
regards
Antti
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http://palosaari.fi/
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