74 lines
2.4 KiB
Plaintext
74 lines
2.4 KiB
Plaintext
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@TEMPLATE decoder_tmpl.c
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Decode With Drops Example
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=========================
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
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This is an example utility which drops a series of frames, as specified
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on the command line. This is useful for observing the error recovery
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features of the codec.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
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Usage
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-----
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This example adds a single argument to the `simple_decoder` example,
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which specifies the range or pattern of frames to drop. The parameter is
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parsed as follows:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ USAGE
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if(argc!=4)
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die("Usage: %s <infile> <outfile> <N-M|N/M>\n", argv[0]);
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{
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char *nptr;
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n = strtol(argv[3], &nptr, 0);
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m = strtol(nptr+1, NULL, 0);
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is_range = *nptr == '-';
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if(!n || !m || (*nptr != '-' && *nptr != '/'))
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die("Couldn't parse pattern %s\n", argv[3]);
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}
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ USAGE
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Dropping A Range Of Frames
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--------------------------
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To drop a range of frames, specify the starting frame and the ending
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frame to drop, separated by a dash. The following command will drop
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frames 5 through 10 (base 1).
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$ ./decode_with_drops in.ivf out.i420 5-10
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Dropping A Pattern Of Frames
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----------------------------
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To drop a pattern of frames, specify the number of frames to drop and
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the number of frames after which to repeat the pattern, separated by
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a forward-slash. The following command will drop 3 of 7 frames.
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Specifically, it will decode 4 frames, then drop 3 frames, and then
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repeat.
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$ ./decode_with_drops in.ivf out.i420 3/7
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Extra Variables
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---------------
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This example maintains the pattern passed on the command line in the
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`n`, `m`, and `is_range` variables:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_VARS
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int n, m, is_range;
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_VARS
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Making The Drop Decision
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------------------------
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The example decides whether to drop the frame based on the current
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frame number, immediately before decoding the frame.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE
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if((is_range && frame_cnt >= n && frame_cnt <= m)
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||(!is_range && m - (frame_cnt-1)%m <= n)) {
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putc('X', stdout);
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continue;
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}
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putc('.', stdout);
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fflush(stdout);
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE
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