Method of multiplexing H.264 elementary streams without timing information coded
Embodiments of the present invention multiplex elementary streams without timing information coded to create a transport stream. In some embodiments, ‘n’ number of access units are constructed and pushed into a list one by one. Each access unit is capable of looking ahead to obtain information on timing for the next access unit. A header is constructed by calculating timing information from the topmost access unit of the list. Said header is written in the transport stream and the remaining bytes of the transport stream are filled with data from the said elementary stream. Thus the transport stream is constructed.
1. A method for multiplexing high definition video elementary streams that do not have timing information coded to create a transport stream (TS), the method comprising the steps of:
constructing ‘n’ number of access units (AU) in a list, each AU capable of looking ahead to obtain information on timing for the next AU, including
reading the elementary stream from the start while converting elementary streams to packetized elementary streams (PES) until it forms a single AU and noting its start and end points,
pushing the just formed single AU into the list,
checking primary picture type coded in the AU pushed into the list,
calculating the timing information including a presentation time stamp (PTS), a decode time stamp (DTS), and deriving variable frame rate (tc) for the elementary streams,
calculating dts(n)=dts(n−1)+tc, and
pts(n)=dts(n) if the primary picture type coded is a B frame, and
decoding B frames and presenting at the same time without including any offset between pts and dts of the B frames,
calculating dts(n)=dts(n−1)+tc, and
pts(n)=dts(n)+pts_offset*tc if the primary picture coded type is an I or P frame, and checking next access units for the number of B frames (pts_offset) that precede before the next I or P frames occurs, and
constructing a next AU and pushing the next AU into the list for repeating the steps of calculating timing information;
initiating a pointer to indicate start of an AU from the list;
iteratively checking start of an AU from the list;
constructing a header by calculating timing information from the topmost AU of the list;
writing the header in the TS; and
filling the remaining bytes of TS with data from an elementary stream.
2. The method as in claim 1 wherein the high definition elementary streams are H.264/AVC video elementary streams.
3. The method as in claim 1 wherein the TS is an MPEG-2 TS.
4. The method as in claim 1 wherein the multiplexing is multiplexing of H.264 video elementary streams which do not have either NAL/VCL-HRD parameters coded (as part of VUI information of the Sequence Parameter Set) or Supplemental Enhancement Information (SEI).
5. The method as in claim 1 wherein picture type (B, P, or I) information is used to calculate the PTS and DTS values of the Packetized Elementary Stream (PES).
6. The method as in claim 1 wherein variable tc is frame rate or field rate and is derived as tc=num_units_in_tick/time_scale.
7. The method as in claim 1 wherein PES packets are broken into fixed 188 byte TS packets.
8. An apparatus comprising circuitry for multiplexing high definition video elementary streams that do not have timing information coded to create a transport stream (TS) according to the steps of:
constructing ‘n’ number of access units (AU) in a list, each AU looking ahead to obtain information on timing for the next AU, including
reading the elementary stream from the start while converting elementary streams to packetized elementary streams (PES) until it forms a single AU and noting its start and end points,
pushing the just formed single AU into the list,
checking primary picture type coded in the AU pushed into the list,
calculating the timing information further including a presentation time stamp (PTS), a decode time stamp (DTS), and deriving variable frame rate (tc) for the elementary streams,
calculating dts(n)=dts(n−1)+tc, and
pts(n)=dts(n) if the primary picture type coded is a B frame, and
decoding B frames and presenting at the same time without including any offset between pts and dts of the B frames,
calculating dts(n)=dts(n−1)+tc, and
pts(n)=dts(n)+pts_offset*tc if the primary picture coded type is an I or P frame, and checking next access units for the number of B frames (pts_offset) that precede before the next I or P frames occurs, and
constructing a next AU and pushing the next AU into the list for repeating the steps of calculating timing information,
initiating a pointer to indicate start of an AU from the list;
iteratively checking start of an AU from the list;
constructing a header by calculating the timing information from the topmost AU of the list;
writing the header in the TS; and
filling the remaining bytes of TS with data from an elementary stream.
9. The apparatus in claim 8 wherein the high definition elementary streams are H.264/AVC video elementary streams.
10. The apparatus in claim 8 wherein the TS is an MPEG-2 TS.
11. The apparatus in claim 8 wherein the multiplexing is multiplexing of H.264 video elementary streams which do not have either NAL/VCL-HRD parameters coded (as part of VUI information of the Sequence Parameter Set) or Supplemental Enhancement Information (SEI).
12. The apparatus as in claim 8 wherein picture type (B, P, or I) information is used to calculate the PTS and DTS values of the Packetized Elementary Stream (PES).
13. The apparatus as in claim 8 wherein variable tc is frame rate or field rate and is derived as tc=num_units_in_tick/time_scale.
14. The apparatus as in claim 8 wherein PES packets are broken into fixed 188 byte TS packets.