1MP4(3)                      MP4 File Format Library                     MP4(3)
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NAME

6       MP4AddRtpVideoHint - Add an RTP video specific hint
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SYNTAX

9       #include <mp4.h>
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11       bool MP4AddRtpVideoHint(
12            MP4FileHandle hFile,
13            MP4TrackId trackId,
14            bool isBFrame = false,
15            u_int32_t timestampOffset = 0
16       );
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ARGUMENTS

19       hFile  Specifies the mp4 file to which the operation applies.
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21       trackId
22              Specifies the hint track to which the operation applies.
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24       isBFrame
25              Specifies if this hint will contain packets for a video B frame
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27       timestampOffset
28              Specifies a positive offset to add to the RTP timestamp for this
29              hint. Caveat: the value is in the hint track timescale.
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RETURN VALUES

32       Upon success, true (1). Upon an error, false (0).
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DESCRIPTION

35       MP4AddRtpVideoHint is an extended version of MP4AddRtpHint specifically
36       to handle MPEG video frames.
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38       The  isBFrame parameter allows the packets in the RTP hint to be marked
39       as belonging to a video B frame. This can  be  useful  to  a  streaming
40       server if packets must be dropped due to system load or network conges‐
41       tion. No other video frames are dependent on the contents of B  frames,
42       so they are least damaging type of frames to drop.
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44       The  timestampOffset  parameter allows an offset to be added to the RTP
45       timestamp of the packets in the RTP hint. This is  necessary  for  MPEG
46       video that contains B frames since the video frames are transmitted out
47       of order with respect to when they should be  rendered.  I.e  I  and  P
48       frames are transmitted before any B frames that depend on them. The RTP
49       timestamp must represent the rendering time of the data in the  packets
50       hence an offset must be added.
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52       Note:  The timestampOffset is equivalent to the sample rendering offset
53       of a video media track. See MP4GetSampleRenderingOffset().
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SEE ALSO

57       MP4(3) MP4AddRtpHint(3) MP4AddRtpPacket(3) MP4WriteRtpHint (3)
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61Cisco Systems Inc.                Version 0.9                           MP4(3)
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