Utkarsh
24th July 2008, 10:40
I have generated .3gp and .mp4 file with timed text track using MP4Box. I have seen the contents of the file. Please find below my observations:
1) The timed text track has been signaled as 'tx3g'.
2) The esds is not present in file. So, streamType and objectTypeIndication are not signaled in the files.
3) The mdat contains text samples. Each text sample is made up of length of the text string followed by text string. Text sample may or may not have text modifiers. The content of text sample in mdat was as per 3GPP TS 26.245.
4) Why MP4Box has not generated TTUs?
I was having following queries:
1) In which case the timed text track will be signaled as 'mp4s'? (MPEG-4 Part 17 -- ISO/IEC 14496-17)
2) How the streamType and objectTypeIndication will be signaled as esds is not present? As per ISO/IEC 14496-17, timed text will be signaled by streamType and objectTypeIndication.
3) Are TTUs generated by some tool? OR TTUs are alreay present in the file inside mdat box?
Are TTUs generated by some packetizer tool? The packetizer tool gets the offset and size of text sample from moov and read the text sample. The text sample is made up of text string and text modifiers. The packetizer tool makes TTUs out of these text samples and streams it over the network.
OR
TTUs are part of mdat. If they are part of mdat then how the TTU's presence will be signaled.
4) Why MP4Box has not generated TTUs?
Any help for answering these queries would be very useful.
Thanks in Advance...
1) The timed text track has been signaled as 'tx3g'.
2) The esds is not present in file. So, streamType and objectTypeIndication are not signaled in the files.
3) The mdat contains text samples. Each text sample is made up of length of the text string followed by text string. Text sample may or may not have text modifiers. The content of text sample in mdat was as per 3GPP TS 26.245.
4) Why MP4Box has not generated TTUs?
I was having following queries:
1) In which case the timed text track will be signaled as 'mp4s'? (MPEG-4 Part 17 -- ISO/IEC 14496-17)
2) How the streamType and objectTypeIndication will be signaled as esds is not present? As per ISO/IEC 14496-17, timed text will be signaled by streamType and objectTypeIndication.
3) Are TTUs generated by some tool? OR TTUs are alreay present in the file inside mdat box?
Are TTUs generated by some packetizer tool? The packetizer tool gets the offset and size of text sample from moov and read the text sample. The text sample is made up of text string and text modifiers. The packetizer tool makes TTUs out of these text samples and streams it over the network.
OR
TTUs are part of mdat. If they are part of mdat then how the TTU's presence will be signaled.
4) Why MP4Box has not generated TTUs?
Any help for answering these queries would be very useful.
Thanks in Advance...