[asterisk-bugs] [JIRA] (ASTERISK-27959) [patch] Asterisk 15.4.1 h264 fmtp negotiation problem

[Kevin Harwell (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-27959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=244082#comment-244082 ] 

Kevin Harwell commented on ASTERISK-27959:
------------------------------------------

[~dvdkhlng], thanks for the detailed report and diagnosis. Unfortunately we cannot accept patches without a [license agreement|https://wiki.asterisk.org/wiki/display/AST/Digium+License+Agreement] (thus why your patch was removed). If you'd like to submit a patch a [Digium License Agreement|https://issues.asterisk.org/jira/secure/DigiumLicense.jspa] will first need to be signed.

If you do choose to go that route, and you'd like your contribution to be included faster, you should submit your patch for code review by the Asterisk Developer Community. To do so, please follow the Code Review [1] instructions on the wiki. Be sure to:
* Verify that your patch conforms to the Coding Guidelines [2]
* Review the Code Review Checklist [3] for common items reviewers will look for
* If necessary, provide tests for the Asterisk Test Suite that verify the correctness of your patch [4]

When ready, submit your patch and any tests to Gerrit [5] for code review.

Thanks!

[1] https://wiki.asterisk.org/wiki/display/AST/Code+Review
[2] https://wiki.asterisk.org/wiki/display/AST/Coding+Guidelines
[3] https://wiki.asterisk.org/wiki/display/AST/Code+Review+Checklist
[4] https://wiki.asterisk.org/wiki/display/AST/Asterisk+Test+Suite+Documentation
[5] https://wiki.asterisk.org/wiki/display/AST/Gerrit+Usage

> [patch] Asterisk 15.4.1 h264 fmtp negotiation problem
> -----------------------------------------------------
>
>                 Key: ASTERISK-27959
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-27959
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Resources/res_format_attr_h264
>    Affects Versions: 15.4.1
>         Environment: Debian Stretch amd64
>            Reporter: David Kuehling
>
> Hi,
> I'm trying to have a bunch of GXV3240, GXV3275 and GXV3140 telephones perform video-telephony via Asterisk.  The Asterisk 13 that's shipping with Debian did have severe problems correctly handling h264 fmtp negotiation, so I am currently investigating how much the latest upstream Asterisk release improves on that.
> Asterisk 15.4.1 is much better, now passing fmtp headers between all those video phones in the SDP.  However, I think there is one problem with how the {{profile-level-id}} attribute is handled:
> Looking at the logs, I can see that my GXV3240 phone sends a fmtp header for video:
> {noformat}
>     a=fmtp:99 profile-level-id=4D0016; packetization-mode=1
> {noformat}
> When Asterisk now relays the request to the target of the call (a GXV3140), the profile-evel-id field gets dropped:
> {noformat}
>     a=fmtp:99 packetization-mode=1
> {noformat}
> Which is a problem for some of these phones, as it makes them revert to very basic video codec parameters (the GXV3240 seem to go down to transmit QCIF when called without profile-level-id).
> Looking at the source code, it is quite obvious what happens here:
> There is a check in res_format_attr_h264.c that only outputs {{profile-level-id}}, if all its components are non-zero.  Howver, note how the GXV3240 has a zero for PROFILE_IOP (the middle byte):
> {code:java}
>     if (attr->PROFILE_IDC && attr->PROFILE_IOP && attr->LEVEL) {
> {code}
> To my untrained eye it looks like this should read
> {code:java}
>     if (attr->PROFILE_IDC || attr->PROFILE_IOP || attr->LEVEL) {
> {code}
> And patching asterisk accordingly makes it correctly pass the {{profile-level-id}}.
> Other phones (like the GVX3140) do not transmit any zeros in {{profile-level-id}}, so are not affected by the problem.
> However, note that I don't know anything about how fmtp negotiation is defined in the standard, so maybe my naive interpretation misses something here.
> cheers,
> David
> PS: will attach patch below



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