RTP profile: unscaled TS shall always be encoded with W-LSB in UO* packets

Bug #1208900 reported by Didier Barvaux on 2013-08-06
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
rohc
Status tracked in Rohc-main
Rohc-1.5.x
Medium
Didier Barvaux
Rohc-1.6.x
Medium
Didier Barvaux
Rohc-main
Medium
Didier Barvaux

Bug Description

According to RFC 4815, §4.1 (https://tools.ietf.org/html/rfc4815#section-4.1):

   RTP Timestamp (TS) values are always encoded using W-LSB encoding,
   both when sent scaled and unscaled. When no TS bits are transmitted
   in a compressed packet, TS is always scaled. If a compressed packet
   carries an Extension 3 and field(Tsc)=0, the compressed packet must
   thus always carry unscaled TS bits. For TS values sent in Extension
   3, W-LSB encoded values are sent using the self-describing variable-
   length format (RFC 3095-Section 4.5.6), and this applies to both
   scaled and unscaled values.

The TS bits in UO* packets shall always be transmitted encoded with W-LSB. W-LSB encoding shall be used if TS is scaled or unscaled.

As of 1.6.0, the ROHC library does use W-LSB for scaled TS but not for unscaled TS. This is not RFC compliant.

Thanks to Fabrice Bellard for reporting the problem.

Didier Barvaux (didier-barvaux) wrote :

Branch 1.5.x is affected.

Didier Barvaux (didier-barvaux) wrote :

Branch 1.6.x is affected.

Didier Barvaux (didier-barvaux) wrote :

Dev branch is affected.

Didier Barvaux (didier-barvaux) wrote :

Bug won't be fixed on 1.5.x and 1.6.x branches because the fixes changes the ROHC packet format. This is forbidden between 1.5.x and 1.6.x releases.

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