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

Bug #1208900 reported by Didier Barvaux
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.

Revision history for this message
Didier Barvaux (didier-barvaux) wrote :

Branch 1.5.x is affected.

Revision history for this message
Didier Barvaux (didier-barvaux) wrote :

Branch 1.6.x is affected.

Revision history for this message
Didier Barvaux (didier-barvaux) wrote :

Dev branch is affected.

Revision history for this message
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.

Revision history for this message
Didier Barvaux (didier-barvaux) wrote :
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