12 Media Stream Recording

26.2443GPP3GPP file format (3GP)Release 17Transparent end-to-end Packet-switched Streaming Service (PSS)TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

12.1 Unprotected Stream Recording

Received RTP media streams may be stored in 3GP files conforming to the Media Stream Recording profile. RTP packets may be stored in RTP reception hint tracks. RTCP packets may be stored in RTCP reception hint tracks.

12.2 Protected Stream recording

SRTP protected media may be stored in 3GP files conforming to the 3GP Media Stream Recording Profile. SRTP and corresponding SRTCP packets are stored in SRTP reception hint tracks and SRTCP reception hint tracks, respectively, as described in [38]. Corresponding MIKEY MBMS Traffic Key messages are stored in OMA BCAST STKM tracks as described in clause 12.2.1. Additionally, SDP and Protection Description information is stored as described in clauses 12.3 and 12.2.2.

12.2.1 Key message tracks

MIKEY MBMS Traffic Key messages as defined in [39] shall be stored in OMA BCAST STKM tracks ‘oksd’ as defined in [37]. A 3GP file with SRTP recording extensions shall contain at least one STKM track. Furthermore, all key messages related a specific SRTP reception hint track shall be recorded in the same STKM track. Track references of type ‘cdsc’ shall be used to link STKM tracks to SRTP reception hint tracks as described in [37].

In the Sample Description Entry of the STKM track, the filed sample_version shall be set to 0x00 and the field sample_type shall be set to 0xf7. The value 0xf7 indicates MIKEY MBMS Traffic Key messages.

Each Sample Entry of a STKM track shall contain exactly one MIKEY MBMS Traffic Key messages in the STKM field. That is, the STKM field shall contain the payload of the received MIKEY package (without IP and UDP headers) including all MIKEY headers and all MIKEY payloads and the MIKEY MAC/Signature field.

12.2.2 Protection Description

The ServiceProtectionDescription box shall be defined as stated in table 12.1. The ServiceProtectionDescription box shall be included for each Sample Description Entry of a SRTP reception hint track as a sub box of the SchmeInformationBox ‘schi’ in the SRTPProcessBox box ‘srpp’ as defined in [7].

Table 12.1: ServiceProtectionDescription box

Field	Type	Details	Value
BoxHeader.Size	Unsigned int(32)
BoxHeader.Type	Unsigned int(32)		‘spdb’
BoxHeader.Version	Unsigned int(8)		0
SecurityDescription	Unsigned int(8)[]	Service Protection Description Metadata Fragment

BoxHeader Size, Type, Version: indicate the size, type and version of the ServiceProtectionDescription box. The type shall be ‘spdb’ and the version shall be 0.

SecurityDescription:. This field shall contain the XML encoded Service Protection Description Metadata Fragment as specified in [40] with the restriction that only the mediaFlow element referring to the SRTP stream from which this SRTP reception hint track was recorded is contained. That is, the SecurityDescription shall contain exactly one mediaFlow element and this element shall correspond to the stored SRTP packets described by the Sample Description which also contains this SecurityDescription.

12.3 SDP

Fragments that together constitute an SDP description shall be contained in a 3GP file with Media Stream recording extensions. Session-level SDP, i.e. all lines before the first media-specific line ("m=" line), shall be stored as Movie SDP information within the User Data box, as specified in [7]. Media-level SDP, i.e. an "m=" line and the lines before the next "m=" line (or end of SDP) shall be stored as Track SDP information within the User data box of the corresponding track. Media-level SDP shall be contained in each corresponding reception hint track or media track.