TT-USB2.0 and high bitrate packet loss (DVB-C/T)

Hi there,

I need to get in concat with someone that can handle, test and review a patch for TT-USB2.0. I've found that for certain high-bitrate streams, the TT-USB2.0 sends more ISOCHRONOUS MPEG data than is specified in the wMaxPacketSize fields. I have a USB analyzer capture which shows this clearly. This of course won't be received at the USB host and packet drops appear inside the stream. The solution is to use another alternate setting. The technotrend chip has many of these. I've now tested using alternate setting 7 instead of 3.

Alternate setting 7 allows transferring a maximum of 3 * 1024 bytes. Alternate setting 3 allows transferring a maximum of 1 * 940 bytes.

--HPS

Quoted 11 lines · Hans Petter Selasky

Hi there,

I need to get in concat with someone that can handle, test and review a patch for TT-USB2.0. I've found that for certain high-bitrate streams, the TT-USB2.0 sends more ISOCHRONOUS MPEG data than is specified in the wMaxPacketSize fields. I have a USB analyzer capture which shows this clearly. This of course won't be received at the USB host and packet drops appear inside the stream. The solution is to use another alternate setting. The technotrend chip has many of these. I've now tested using alternate setting 7 instead of 3.

Quoted 4 lines

Alternate setting 7 allows transferring a maximum of 3 * 1024 bytes. Alternate setting 3 allows transferring a maximum of 1 * 940 bytes.

--HPS

Hi,

It turns out that this device, at least the version I bought, does not work with the XHCI at all when using multi-packet transfers, alternate setting 7, because DATA2 PID is used when transfer is less than 1024 bytes. It should be DATA0 PID first, then 1 and 2 in the end. Probably a firmware update can fix this, but I'm not aware about if such exists. The PID issue was found using a USB analyzer.

Apparently this bug has gone undetected, because at least the EHCI high speed only controller I've got silently ignores this kind of errors and receives the data whilst the XHCI not. Conclusion:
Existing alternate setting must be used.

I think I will have to get another USB based receiver with CI slot. Any recommendations for DVB-T ?

Quoted 2 lines · Hans Petter Selasky

I think I will have to get another USB based receiver with CI slot. Any recommendations for DVB-T ?

There is no many alternatives available. I suspect Anysee E7 serie is the only one. And I am not even sure if its CI works anymore. Lastly when I tested it I didn't get scrambled channels working - but it could be due to card entitlements were not upgraded. Anyhow, if there is bug then it should be easy to fix.