Quicktime File Format (2012-08-14).pdf

Media Data Atom TypesPacketization Hint Sample Data for Data Format 'rtp 'first_sample_in_this_chunk = 1; /* also calculated from that atom */chunk_offset = chunk_offsets[chunk_number]; /* from the stco atom */data_offset = (sample_number - first_sample_in_this_chunk) * BPCB/ SPCB;read_from_file(chunk_offset + data_offset, length); /* read our data */Sample Description ModeThe data table entry has the format for sample description mode shown in Figure 4-20 (page 266).Figure 4-20Sample description mode format0 1 2 3 4 5 6 7 8 9 0 1 2 3 4data source = 3track ref indexlength5sample description indexoffsetreservedField descriptionsData source = 3A value of 3 indicates that the data is to be taken from the media track's sample description table.Track ref indexA value that indicates which track the sample description will come from. A value of 0 means that thereis exactly one hint track reference, so use that. Values from 1 to 127 are indexes into the hint track referenceatom entries, indicating which original media track the sample is to be read from. A value of -1 meansthe hint track itself, that is, get the sample description from the same track as the hint sample you arecurrently parsing.LengthA 16-bit integer specifying the number of bytes to copy.Sample description indexA 32-bit integer specifying the index into the media's sample description table.OffsetA 32-bit integer specifying the offset from the start of the sample description from which to start copying.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.266