rohc

modify the feedback system in O-mode

Asked by qingbaibai on 2012-03-20

hello,

I try to modify the feedback system. I mainly change three files : rohc_decomp.h/c and d_generic.c. I set the situation "ROHC_ERROR" to "ROHC_ERROR_CRC", ie, if decompression is failure, it always returns ROHC_ERROR_CRC. I change feedback from piggybacking to interspersing. So I add ROHC_ERROR_FEEDBACK when feedback is decompressed unsuccessfully.
Here are the main code:

first, in file rohc_decomp.h
add #define N and #define K

in struct d_context add:
/// create a window for feedback interval in NO CONTEXT state
    struct c_wlsb *curvalnc;
    /// create a window for feedback interval in STATIC CONTEXT state
    struct c_wlsb *curvalsc;
    /// create a window for feedback interval in FULL CONTEXT state
    struct c_wlsb *curvalfc;
    /// create a window for feedback interval in case of ROHC_ERROR_NO_CONTEXT
    struct c_wlsb *curvalenc;
     /// create a window for feedback interval in STATIC CONTEXT state
    struct c_wlsb *curvalsc0;
    ///The number of received packets in NO CONTEXT state
    int num_recv_nc;
    ///The number of received packets in STATIC CONTEXT state
    int num_recv_sc;
    ///The number of received packets in FULL CONTEXT state
    int num_recv_fc;
    ///The number of received packets in case of ROHC_ERROR_CONTEXT
    int num_recv_enc;
    ///The number of received packets in STATIC CONTEXT state(type0,1)
    int num_recv_sc0;

second, in file rohc_decomp.c
in function rohc_decompress():
switch(ret)
{
        case ROHC_ERROR_PACKET_FAILED:
        break;
        //BY SQ
        case ROHC_ERROR_FEEDBACK:
        break;
        case ROHC_ERROR_CRC:
            decomp->statistics.packets_failed_crc++;
            switch(ddata.active->state)
            {
            case NO_CONTEXT:
                ddata.active->num_recv_nc++;
                rohc_debugf(2, "num_recv_nc = %d\n", ddata.active->num_recv_nc);
                c_add_wlsb(ddata.active->curvalnc, 0, 0, 1);
                if(ddata.active->num_recv_nc >= N && c_sum_wlsb(ddata.active->curvalnc)>= K &&
                   c_sum_wlsb(ddata.active->curvalnc) <= N)
                {
                    int i;
                    //set wlsb window value to zero
                    for(i = 0; i < N; i++)
                    {
                        c_add_wlsb(ddata.active->curvalnc, 0, 0, 0);
                        ddata.active->curvalnc->next--;
                        ddata.active->curvalnc->window[ddata.active->curvalnc->next].used = ROHC_FALSE;
                        ddata.active->curvalnc->next++;
                    }
                    ddata.active->curvalnc->next = 0;
                    ddata.active->curvalnc->oldest = 0;
                    ddata.active->num_recv_nc = 0;

                    rohc_debugf(2, "feedback curr %d\n", c_sum_wlsb(ddata.active->curvalnc));
           rohc_debugf(2, "feedback max %d no context\n", N);
                    d_operation_mode_feedback(decomp, ROHC_ERROR_CRC, ddata.cid,
                              ddata.addcidUsed, ddata.largecidUsed,
                              ddata.active->mode, ddata.active);
                }
                break;
            case STATIC_CONTEXT:
                ddata.active->num_recv_sc++;
                rohc_debugf(2, "num_recv_sc = %d\n", ddata.active->num_recv_sc);
                c_add_wlsb(ddata.active->curvalsc, 0, 0, 1);
                if(ddata.active->num_recv_sc >= N && c_sum_wlsb(ddata.active->curvalsc)>= K &&
                   c_sum_wlsb(ddata.active->curvalsc) <= N)
                {
                    int i;
                    //set wlsb window value to zero
                    for(i = 0; i < N; i++)
                    {
                        c_add_wlsb(ddata.active->curvalsc, 0, 0, 0);
                        ddata.active->curvalsc->next--;
                        ddata.active->curvalsc->window[ddata.active->curvalsc->next].used = ROHC_FALSE;
                        ddata.active->curvalsc->next++;
                    }
                    ddata.active->curvalsc->next = 0;
                    ddata.active->curvalsc->oldest = 0;
                    ddata.active->num_recv_sc = 0;

                    rohc_debugf(2, "feedback curr %d\n", c_sum_wlsb(ddata.active->curvalsc));
           rohc_debugf(2, "feedback max %d static context %d\n", N);
                    d_operation_mode_feedback(decomp, ROHC_ERROR_CRC, ddata.cid,
                              ddata.addcidUsed, ddata.largecidUsed,
                              ddata.active->mode, ddata.active);
                }
                break;
            case FULL_CONTEXT:
                ddata.active->num_recv_fc++;
                rohc_debugf(2, "num_recv_fc = %d\n", ddata.active->num_recv_fc);
                c_add_wlsb(ddata.active->curvalfc, 0, 0, 1);
                if(ddata.active->num_recv_fc >= N && c_sum_wlsb(ddata.active->curvalfc)>= K &&
                   c_sum_wlsb(ddata.active->curvalfc) <= N)
                {
                    int i;
                    //set wlsb window value to zero
                    for(i = 0; i < N; i++)
                    {
                        c_add_wlsb(ddata.active->curvalfc, 0, 0, 0);
                        ddata.active->curvalfc->next--;
                        ddata.active->curvalfc->window[ddata.active->curvalfc->next].used = ROHC_FALSE;
                        ddata.active->curvalfc->next++;
                    }
                    ddata.active->curvalfc->next = 0;
                    ddata.active->curvalfc->oldest = 0;
                    ddata.active->num_recv_fc = 0;

                    rohc_debugf(2, "feedback curr %d\n", c_sum_wlsb(ddata.active->curvalfc));
           rohc_debugf(2, "feedback max %d full context\n", N);
                    d_operation_mode_feedback(decomp, ROHC_ERROR_CRC, ddata.cid,
                              ddata.addcidUsed, ddata.largecidUsed,
                              ddata.active->mode, ddata.active);
                }
                break;

}

  case ROHC_ERROR_NO_CONTEXT:
   decomp->statistics.packets_failed_no_context++;
            ddata.active->num_recv_enc++;
            rohc_debugf(2, "num_recv_enc = %d\n", ddata.active->num_recv_enc);
            c_add_wlsb(ddata.active->curvalenc, 0, 0, 1);
            if(ddata.active->num_recv_enc >= N && c_sum_wlsb(ddata.active->curvalenc)>= K &&
            c_sum_wlsb(ddata.active->curvalenc) <= N)
            {
                int i;
                //set wlsb window value to zero
                for(i = 0; i < N; i++)
                {
                    c_add_wlsb(ddata.active->curvalenc, 0, 0, 0);
                    ddata.active->curvalenc->next--;
                    ddata.active->curvalenc->window[ddata.active->curvalenc->next].used = ROHC_FALSE;
                    ddata.active->curvalenc->next++;
                }
                ddata.active->curvalenc->next = 0;
                ddata.active->curvalenc->oldest = 0;
                ddata.active->num_recv_enc = 0;

                rohc_debugf(2, "feedback curr %d\n", c_sum_wlsb(ddata.active->curvalenc));
       rohc_debugf(2, "feedback max %d error no context\n", N);
                d_operation_mode_feedback(decomp, ROHC_ERROR_NO_CONTEXT, ddata.cid,
                              ddata.addcidUsed, ddata.largecidUsed,
                              O_MODE, NULL);
                }
   break;

        case ROHC_ERROR_SC:
   ddata.active->num_recv_sc0++;
            rohc_debugf(2, "num_recv_sc0 = %d\n", ddata.active->num_recv_sc0);
            c_add_wlsb(ddata.active->curvalsc0, 0, 0, 1);
            if(ddata.active->num_recv_sc0 >= N && c_sum_wlsb(ddata.active->curvalsc0)>= K &&
            c_sum_wlsb(ddata.active->curvalsc0) <= N)
            {
                int i;
                //set wlsb window value to zero
                for(i = 0; i < N; i++)
                {
                    c_add_wlsb(ddata.active->curvalsc0, 0, 0, 0);
                    ddata.active->curvalsc0->next--;
                    ddata.active->curvalsc0->window[ddata.active->curvalsc0->next].used = ROHC_FALSE;
                    ddata.active->curvalsc0->next++;
                }
                ddata.active->curvalsc0->next = 0;
                ddata.active->curvalsc0->oldest = 0;
                ddata.active->num_recv_sc0 = 0;

                rohc_debugf(2, "feedback curr %d\n", c_sum_wlsb(ddata.active->curvalsc0));
       rohc_debugf(2, "feedback max %d sc(recieve type1,0)\n", N);
                d_operation_mode_feedback(decomp, ROHC_ERROR_NO_CONTEXT, ddata.cid,
                              ddata.addcidUsed, ddata.largecidUsed,
                              O_MODE, NULL);
                }
   break;

  default: /* ROHC_OK_NO_DATA, ROHC_OK */
   if(decomp->compressor != NULL && decomp->ack_sent < MAX_ACK)
   {
    /* switch active context to O-mode */
    ddata.active->mode = O_MODE;
    d_operation_mode_feedback(decomp, ROHC_OK, ddata.cid, ddata.addcidUsed,
                              ddata.largecidUsed, ddata.active->mode,
                              ddata.active);
                decomp->ack_sent++;
                rohc_debugf(2, "the number of transition ack is %d\n", decomp->ack_sent);
   }
   break;
}

in function d_optimistic_feedback():
switch(rohc_status)
{
  case ROHC_OK:
   /* create an ACK feedback */
   rohc_debugf(1, "send an ACK feedback\n");
   f_feedback2(ACKTYPE_ACK, context->mode, context->profile->get_sn(context), &sfeedback);
   feedback = f_wrap_feedback(&sfeedback, cid, largecidUsed, WITH_CRC, &feedbacksize);
   if(feedback == NULL)
   {
    rohc_debugf(0, "failed to create an ACK feedback\n");
    return;
   }

   /* send the feedback via the compressor associated
    * with the decompressor */
   context->num_sent_feedbacks++;
   c_piggyback_feedback(decomp->compressor, feedback, feedbacksize);

   /* destroy the feedback */
   zfree(feedback);
   break;

  case ROHC_ERROR_NO_CONTEXT:
   /* create a STATIC NACK feedback */
   rohc_debugf(1, "send a STATIC NACK feedback\n");
   f_feedback2(ACKTYPE_STATIC_NACK, O_MODE, 0, &sfeedback);
   f_add_option(&sfeedback, OPT_TYPE_SN_NOT_VALID, NULL);
   feedback = f_wrap_feedback(&sfeedback, cid, largecidUsed, NO_CRC, &feedbacksize);
   if(feedback == NULL)
   {
    rohc_debugf(0, "failed to create a STATIC NACK feedback\n");
    return;
   }

   /* send the feedback via the compressor associated
    * with the decompressor */
   context->num_sent_feedbacks++;
   c_piggyback_feedback(decomp->compressor, feedback, feedbacksize);

   /* destroy the feedback */
   zfree(feedback);
   break;

        case ROHC_ERROR_SC:
            if(context->state != STATIC_CONTEXT)
            {
               return;
            }
            /* create a NACK feedback */
   rohc_debugf(1, "send a NACK feedback\n");
   f_feedback2(ACKTYPE_NACK, context->mode, context->profile->get_sn(context), &sfeedback);
   feedback = f_wrap_feedback(&sfeedback, cid, largecidUsed, WITH_CRC, &feedbacksize);
   if(feedback == NULL)
   {
       rohc_debugf(0, "failed to create a NACK feedback\n");
       return;
   }

   /* send the feedback via the compressor associated
    * with the decompressor */
            context->num_sent_feedbacks++;
      c_piggyback_feedback(decomp->compressor, feedback, feedbacksize);

   /* destroy the feedback */
      zfree(feedback);
            break;

  case ROHC_ERROR_CRC:
   //context->num_sent_feedbacks++;
   switch(context->state)
   {
    case NO_CONTEXT:
     /* create a STATIC NACK feedback */
     rohc_debugf(1, "send a STATIC NACK feedback\n");
     f_feedback2(ACKTYPE_STATIC_NACK, context->mode, context->profile->get_sn(context), &sfeedback);
     feedback = f_wrap_feedback(&sfeedback, cid, largecidUsed, WITH_CRC, &feedbacksize);
     if(feedback == NULL)
     {
      rohc_debugf(0, "failed to create a STATIC NACK feedback\n");
      return;
     }

     /* send the feedback via the compressor associated
      * with the decompressor */
                    context->num_sent_feedbacks++;
     c_piggyback_feedback(decomp->compressor, feedback, feedbacksize);

     /* destroy the feedback */
     zfree(feedback);
     break;

            case STATIC_CONTEXT:
                     /* create a STATIC NACK feedback*/
                    rohc_debugf(1, "send a STATIC NACK feedback\n");
     f_feedback2(ACKTYPE_STATIC_NACK, context->mode, context->profile->get_sn(context), &sfeedback);
     feedback = f_wrap_feedback(&sfeedback, cid, largecidUsed, WITH_CRC, &feedbacksize);
     if(feedback == NULL)
     {
      rohc_debugf(0, "failed to create a STATIC NACK feedback\n");
      return;
     }

                    /* change state */
                    rohc_debugf(1, "change decompressor state from SC to NC");
                    context->state = NO_CONTEXT;

                    /* destroy the feedback */
     zfree(feedback);
                    break;

    case FULL_CONTEXT:
     /* create a NACK feedback */
     rohc_debugf(1, "send a NACK feedback\n");
     f_feedback2(ACKTYPE_NACK, context->mode, context->profile->get_sn(context), &sfeedback);
     feedback = f_wrap_feedback(&sfeedback, cid, largecidUsed, WITH_CRC, &feedbacksize);
     if(feedback == NULL)
     {
      rohc_debugf(0, "failed to create a NACK feedback\n");
      return;
     }

     /* change state */
                    rohc_debugf(1, "change decompressor state from FC to SC");
     context->state = STATIC_CONTEXT;

     /* destroy the feedback */
     zfree(feedback);
     break;

    default:
     rohc_debugf(0, "should not arrive: unknown state value (%d)\n",
                 context->state);
     break;
   }
   break;
}

in function struct d_context * context_create():
context->num_recv_nc = 0;
    context->num_recv_sc = 0;
    context->num_recv_fc = 0;
    context->num_recv_enc = 0;
    context->num_recv_sc0 = 0;
    context->curvalnc = c_create_wlsb(32, N, 0);
    context->curvalsc = c_create_wlsb(32, N, 0);
    context->curvalfc = c_create_wlsb(32, N, 0);
    context->curvalenc = c_create_wlsb(32, N, 0);
    context->curvalsc0 = c_create_wlsb(32, N, 0);

in function context_free():
c_destroy_wlsb(context->curvalnc);
        c_destroy_wlsb(context->curvalsc);
        c_destroy_wlsb(context->curvalfc);
        c_destroy_wlsb(context->curvalenc);
        c_destroy_wlsb(context->curvalsc0);

third, in file d_generic.c
in function decode_generic_decode_ir(), add code before context->state = FULL_CONTEXT:
//set wlsb window value to zero when change state
if(context->state == NO_CONTEXT)
        {
            int i;
            //set wlsb window value to zero
            for(i = 0; i < N; i++)
            {
                c_add_wlsb(context->curvalnc, 0, 0, 0);
                context->curvalnc->next--;
                context->curvalnc->window[context->curvalnc->next].used = ROHC_FALSE;
                context->curvalnc->next++;
            }
            context->curvalnc->next = 0;
            context->curvalnc->oldest = 0;
            context->num_recv_nc = 0;
        }
        else if(context->state == STATIC_CONTEXT)
        {
             int i;
            //set wlsb window value to zero
            for(i = 0; i < N; i++)
            {
                c_add_wlsb(context->curvalsc, 0, 0, 0);
                context->curvalsc->next--;
                context->curvalsc->window[context->curvalsc->next].used = ROHC_FALSE;
                context->curvalsc->next++;
                c_add_wlsb(context->curvalsc0, 0, 0, 0);
                context->curvalsc0->next--;
                context->curvalsc0->window[context->curvalsc0->next].used = ROHC_FALSE;
                context->curvalsc0->next++;
            }
            context->curvalsc->next = 0;
            context->curvalsc->oldest = 0;
            context->num_recv_sc = 0;
            context->curvalsc0->next = 0;
            context->curvalsc0->oldest = 0;
            context->num_recv_sc0 = 0;
        }

in function decode_irdyn, add code after context->state = FULL_CONTEXT:
int i1;
    //set wlsb window value to zero when change state
    for(i1 = 0; i1 < N; i1++)
    {
         c_add_wlsb(context->curvalsc, 0, 0, 0);
         context->curvalsc->next--;
         context->curvalsc->window[context->curvalsc->next].used = ROHC_FALSE;
         context->curvalsc->next++;
         c_add_wlsb(context->curvalsc0, 0, 0, 0);
         context->curvalsc0->next--;
         context->curvalsc0->window[context->curvalsc0->next].used = ROHC_FALSE;
         context->curvalsc0->next++;
    }
    context->curvalsc->next = 0;
    context->curvalsc->oldest = 0;
    context->num_recv_sc = 0;
    context->curvalsc0->next = 0;
    context->curvalsc0->oldest = 0;
    context->num_recv_sc0 = 0;

in function decode_uor2(), add code after context->state = FULL_CONTEXT:
int i1;
    //set wlsb window value to zero when change state
    for(i1 = 0; i1 < N; i1++)
    {
         c_add_wlsb(context->curvalsc, 0, 0, 0);
         context->curvalsc->next--;
         context->curvalsc->window[context->curvalsc->next].used = ROHC_FALSE;
         context->curvalsc->next++;
         c_add_wlsb(context->curvalsc0, 0, 0, 0);
         context->curvalsc0->next--;
         context->curvalsc0->window[context->curvalsc0->next].used = ROHC_FALSE;
         context->curvalsc0->next++;
    }
    context->curvalsc->next = 0;
    context->curvalsc->oldest = 0;
    context->num_recv_sc = 0;
    context->curvalsc0->next = 0;
    context->curvalsc0->oldest = 0;
    context->num_recv_sc0 = 0;

in function d_generic_decode:
in switch(find_packet_type(decomp, context, packet, second_byte)): case PACKET_UO_0, case PACKET_UO_1, case PACKET_UO_1_ID, change "goto error" to "return ROHC_ERROR_SC".

I change the code in that way according to RFC 3095 5.3.2.2.3 and 5.4.2.2.

Question information

Language:: English Edit question

Status:: Open

For:: rohc Edit question

Assignee:: Didier Barvaux Edit question

Last query:: 2012-03-26

Last reply:: 2012-03-20

Revision history for this message

Didier Barvaux (didier-barvaux) said on 2012-03-20:

Hi qingbaibai,

Thanks a lot for your modifications on the code! Better conformance to the
ROHC RFCs is welcome :-)

I had some trouble reading the code you proposed because Launchpad mangled
the spaces and tabulations. Could you prepare a patch and attach it to bug #902465 ?
It should be easier for me to review it.

You can learn how to create a patch with Bazaar (ie. the tool used to manage sources
of the project) in FAQ #640.

If you do not want to use Bazaar, you can generate a patch by hand with the following
commands:
  $ cd <rohc_directory_with_reference_sources>
  $ make distclean
  $ cd ..
  $ cd <rohc_direcory_with_modified_sources>
  $ make distclean
  $ cd ..
  $ diff -Nru <rohc_directory_with_reference_sources> \
     <rohc_direcory_with_modified_sources> > fix_bug_902465.patch

If my explanations are not clear enough, let me know.

Regards,
Didier

Revision history for this message

qingbaibai (sunqing-cztz) said on 2012-03-21:

hello,
I send the full code to you in attachment named rohc-1.3.1 feedback. I change test.c file and add delay for my own purpose. Delay is not related to feedback.Where I change is declared in the previous question. If you can not see my code, please tell me. Thank you.
Regards,qingbaibai

> To: <email address hidden>
> From: <email address hidden>
> Subject: Re: [Question #191211]: modify the feedback system in O-mode
> Date: Tue, 20 Mar 2012 18:40:56 +0000
>
> Your question #191211 on rohc changed:
> https://answers.launchpad.net/rohc/+question/191211
>
> Status: Open => Needs information
>
> Didier Barvaux requested more information:
> Hi qingbaibai,
>
> Thanks a lot for your modifications on the code! Better conformance to the
> ROHC RFCs is welcome :-)
>
> I had some trouble reading the code you proposed because Launchpad mangled
> the spaces and tabulations. Could you prepare a patch and attach it to bug #902465 ?
> It should be easier for me to review it.
>
> You can learn how to create a patch with Bazaar (ie. the tool used to manage sources
> of the project) in FAQ #640.
>
> If you do not want to use Bazaar, you can generate a patch by hand with the following
> commands:
> $ cd <rohc_directory_with_reference_sources>
> $ make distclean
> $ cd ..
> $ cd <rohc_direcory_with_modified_sources>
> $ make distclean
> $ cd ..
> $ diff -Nru <rohc_directory_with_reference_sources> \
> <rohc_direcory_with_modified_sources> > fix_bug_902465.patch
>
> If my explanations are not clear enough, let me know.
>
> Regards,
> Didier
>
> --
> To answer this request for more information, you can either reply to
> this email or enter your reply at the following page:
> https://answers.launchpad.net/rohc/+question/191211
>
> You received this question notification because you asked the question.

Revision history for this message

qingbaibai (sunqing-cztz) said on 2012-03-21:

hello,
I just tested my code and found some bugs and I corrected it. I send the corrected code in attachment named "rohc-1.3.1 feedback final". I test my code under windows with MinGW.
I use voip pcap file. In my test, it sends feedback under ROHC_ERROR_CRC and ROHC_ERROR_SC. The state machine changes from FC to SC and the compressor sends IR-DYN packet. When it stays in SC state, because of delay the decompressor still receives UO-0 packets so it returns ROHC_ERROR_SC. I don't test the situation that the decompressor changes its state from SC to NC.
I have question in when sending feedback with CRC and without CRC. If there is something I don't consider, please tell me. Thank you.
Regards,qingbaibai

Revision history for this message

qingbaibai (sunqing-cztz) said on 2012-03-21:

hello,
I have a question. In RFC 3095 5.7.6.1 : "The sequence number to useis the sequence number of the header which caused the feedbackinformation to be sent. If that sequence number cannot bedetermined, for example when decompression fails, the sequence numberto use is that of the last successfully decompressed header."
Whether the SN used in feedback is the SN of last decompress failed packet?
Regards,qingbaibai

Revision history for this message

Didier Barvaux (didier-barvaux) said on 2012-03-21:

Hello,

I did not receive the code as attachement. Attachements are not supported by questions/answers
on Launchpad. Please, create a patch (follow my previous instructions) and attach it to the bug I
mentioned. Do not attach the full code, it is way too large! A patch is smaller and easier to manage.
If you need some more explanation for that process, tell me.

For you question about SN, I would say that you have to use the SN stored in the decompression
context. This is the SN of the last successfully decompressed packet.

Regards,
Didier

Revision history for this message

qingbaibai (sunqing-cztz) said on 2012-03-21:

hello,
I put my source code file named feedback in "home" folder. I follow FAQ #640 and try to input command " bzr add /home/feedback". This is wrong. Can you interpret in detail about how to create a patch. Thank you.
Regards,qingbaibai

Revision history for this message

Didier Barvaux (didier-barvaux) said on 2012-03-21:

Hello,

> I put my source code file named feedback in "home" folder. I follow
> FAQ #640 and try to input command " bzr add /home/feedback". This
> is wrong. Can you interpret in detail about how to create a patch.

How did you get the source code? Did you use the 'bzr branch lp:rohc'
command?

If yes, 'bzr diff' should work, please send the exact error message you
have.

If you did not use 'bzr branch', you probably downloaded a tar.gz/tar.bz2
archive. In this case, you have to follow the instructions I gave you in my
first answer.

Tell me if my explanations are not clear enough.

Regards,
Didier

Revision history for this message

qingbaibai (sunqing-cztz) said on 2012-03-26:

hello，
There is a new question. When seting MAX_IR_COUNT to 1 and the first IR packet is lost, both the compressor and decompressor are in U-MODE. It returns ROHC_ERROR_NO_CONTEXT. Hence, how could it send feedback if it still works in U-MODE.Thank you.
Regards,qingbaibai

Revision history for this message

Didier Barvaux (didier-barvaux) said on 2012-03-27:

Hello,

Sending feedbacks in U-Mode is normal behaviour according to RFC:
http://tools.ietf.org/html/rfc3095#section-5.3.2.3

If the compressor receives one ACK(U) feedback, it should reduce the frequency
of IR packets. This feature is not implemented yet in the library.

If the compressor receives one ACK(O) feeback, it may transit to O-Mode.

Do you need more help for creating the patch?

Regards,
Didier

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rohc

modify the feedback system in O-mode

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