Hi,

Is it possible to make  "ROHC_WLSB_WIDTH_MAX 256U" in the next release so
that a wide range of  width values can be used in rohc_comp_set_wlsb_window_
width() method?

Is it possible to make  "rohc_lsb_shift_t" values parametric in next
release ? I mean to make lsb shift values parametric so that users can set
any shift value from a related parameter?

Final one is; is it possible to change lsb_width and shift values
dynamically while related compressor/decompressors are in progress?

Best Regards...


2018-02-12 14:39 GMT+03:00 mehmet sulak <mehmet.su...@gmail.com>:

> Hi ,
>
> Thank you for your response,
>
> Here are my changes;
>
> in file interval.h
> //#define ROHC_WLSB_WIDTH_MAX to 64U (comment out)
> #define ROHC_WLSB_WIDTH_MAX 256U  (new definition)
>
> also added new enum value at "rohc_lsb_shift_t"
>
> ROHC_LSB_SHIFT_UDP_SN = 128
>
> to be used in UDP traffic.
>
> also in files c_udp.c and d_udp.c
>
> instead of using  "ROHC_LSB_SHIFT_SN" which is  -1
>
> I used newly defined  "ROHC_LSB_SHIFT_UDP_SN" value
>
>
> For the  trade-off between compression efficiency and robustness I
> observed that for configurations
>
> higher then lsb_w = 32 and p=16 makes UDP/IP header to 7 bytes. So I
> choose the lsb_w=256 and p = 128 for greatest coverage.
>
> Best Regards...
>
>
> 2018-02-08 17:17 GMT+03:00 Didier Barvaux <did...@barvaux.org>:
>
>> Hello,
>>
>> Sorry for not answering sooner. I could have saved you some time about
>> the WLSB width :-/
>>
>> First of all, your changes seem correct. Please send me a patch, I'll
>> check if I can integrate your changes in the next release.
>>
>> The increased size is indeed a consequence. You ask the library to be
>> more robust, so it sends more information to achieve that goal.
>>
>> You have to choose a trade-off between a/ compression efficiency and b/
>> robustness. Did you try to set smaller value for the WLSB width? Maybe
>> 128 provides enough robustness? Maybe 192?
>>
>> Regards,
>> Didier
>>
>>
>> On Tue, 6 Feb 2018 17:31:18 +0300,
>> mehmet sulak <mehmet.su...@gmail.com> wrote:
>>
>> > After some trials I saw that;
>> >
>> > rohc_comp_set_wlsb_window_width()  method is working correctly, the
>> > second parameter is just width of LSB window however I toughed that
>> > it was the number of bits that are for  LSB  width.
>> >
>> > I set it as 256 to handle large number of problematic cases(by setting
>> > ROHC_WLSB_WIDTH_MAX to 256U). Also I set  ROHC_LSB_SHIFT_SN  as 128 to
>> > handle delayed packets.
>> > (I defined new enumeration field whose value is 128 by updating
>> > interval.h and setting new value in c_udp.c and d_udp.c files)
>> >
>> > The results are seems to perfect. Rohc decomress errors are seems to
>> > minimized to very small values which stems from loss of initial
>> > context packages.
>> >
>> > The drawback is that 28 byte UDP headers were compressed to 4 bytes
>> > previously but with the solution that I tried they are now compressed
>> > to 7 bytes.
>> >
>> > Is this normal behavior?
>> >
>> > Best Regards..
>> >
>> >
>> >
>> > 2018-01-30 17:26 GMT+03:00 mehmet sulak <mehmet.su...@gmail.com>:
>> >
>> > > Thanks for your detailed response first;
>> > >
>> > > First I tried method  rohc_comp_set_wlsb_window_width(comp,8) by
>> > > giving 8bits window width but I still observe the following in the
>> > > log files;
>> > >
>> > > rohc_decomp_rfc3095.c:1463 parse_uo0() 4 SN bits = 0xe
>> > >
>> > > So I think it still uses 4 bit window length? If yes did I do
>> > > something wrong?
>> > >
>> > > Secondly I think for UDP packets ROHC_LSB_SHIFT_SN(-1) is used for
>> > > compressor and decompressor which makes parsing delayed packets
>> > > impossible.
>> > >
>> > > So I need to use something half of (2 ^ lsb_width)  instead of -1 by
>> > > adding a new enumeration value.
>> > >
>> > > Do have any idea about this parameter?
>> > >
>> > > Best Regards..
>> > >
>> > > 2018-01-29 22:11 GMT+03:00 Didier Barvaux <did...@barvaux.org>:
>> > >
>> > >> Hello,
>> > >>
>> > >> > I am using Rohc comressor/decomressor pair on a lossy
>> > >> > media(sometimes at receiver side some packets are lost) and the
>> > >> > orderings of the  UDP packets are not guaranteed.(packets are
>> > >> > not coming in right order all the time).
>> > >> >
>> > >> > I am using Unidirectional mode and observe some decomression
>> > >> > failures about CRC check, malformed packets...
>> > >> >
>> > >> > Any recommendation to overcome these issues?
>> > >>
>> > >> The ROHC protocol provides several ways to handle packet loss or
>> > >> reordering:
>> > >>
>> > >> a/ Increasing the width of the window used by the W-LSB algorithm
>> > >>    improves the robustness of the ROHC protocol by sending more
>> > >> bits for changing fields. Given a W-LSB width <wlsb_width>, up to
>> > >>    (<wlsb_width> - 1) packets may be lost without causing
>> > >> additional loss.
>> > >>    The default width is set to 4 by the ROHC library ; please use
>> > >> the rohc_comp_set_wlsb_window_width() function to change the
>> > >> value ; see [1] for more details.
>> > >>
>> > >> b/ Increasing the number of transmissions N required for a changing
>> > >>    static fields or a changing pattern for a dynamic field ensures
>> > >> that the loss of N-1 packets during such a change will cause no
>> > >>    additional loss.
>> > >>    The default number of transmissions is set to 3 by the ROHC
>> > >>    library ; there is no API to change the value at that time, but
>> > >> you may change the value of the constant MAX_IR_COUNT in the
>> > >> source file src/comp/rohc_comp_internals.h and re-build/re-install
>> > >> the library.
>> > >>
>> > >> c/ Same as b/ but for lists of extensions headers (such as IPv6
>> > >>    extension headers, GRE, AH...). Use the function
>> > >>    rohc_comp_set_list_trans_nr() to change the value ; the default
>> > >>    value is set to 5 ; see [2] for more details.
>> > >>
>> > >> d/ You may enable packet/context repair upon CRC failures, so that
>> > >> the decompressor tries to fix the context or packet if it detects a
>> > >>    decompression problem (due to packet loss/reordering for
>> > >> example). The feature is disabled by default. Enable it with the
>> > >> function rohc_decomp_set_features() and the feature
>> > >>    ROHC_DECOMP_FEATURE_CRC_REPAIR ; see [3] for more details.
>> > >>
>> > >> Configuring options a-c is easier if you know the largest number of
>> > >> consecutive losses that you may expect and/or you want to be
>> > >> protected against.
>> > >>
>> > >> Let me know if my explanations are clear enough or if you need more
>> > >> details. And, of course, let me know if one of the options solves
>> > >> your problem.
>> > >>
>> > >> Regards,
>> > >> Didier
>> > >>
>> > >>
>> > >> [1] documentation of rohc_comp_set_wlsb_window_width():
>> > >> https://rohc-lib.org/support/documentation/API/rohc-doc-2.1.
>> > >> 0/group__rohc__comp.html#ga2b68070dddbc038cd55490952a7b3fa4
>> > >>
>> > >> [2] documentation of rohc_comp_set_list_trans_nr():
>> > >> https://rohc-lib.org/support/documentation/API/rohc-doc-2.1.
>> > >> 0/group__rohc__comp.html#ga32608bc06e1b0d1656e463eeb1ccbd7f
>> > >>
>> > >> [3] documentation of rohc_decomp_set_features():
>> > >> https://rohc-lib.org/support/documentation/API/rohc-doc-2.1.
>> > >> 0/group__rohc__decomp.html#ga2298148ca8dc277a1c1905f550f21f7b
>> > >>
>> > >>
>> > >> _______________________________________________
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>> > >
>>
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