ref: d9ca52452bff9481ec1ed4684985a86fb7fc3c3e
dir: /examples/decode_with_drops.txt/
@TEMPLATE decoder_tmpl.c Decode With Drops Example ========================= ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION This is an example utility which drops a series of frames, as specified on the command line. This is useful for observing the error recovery features of the codec. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION Usage ----- This example adds a single argument to the `simple_decoder` example, which specifies the range or pattern of frames to drop. The parameter is parsed as follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ USAGE if(argc!=4) die("Usage: %s <infile> <outfile> <N-M|N/M>\n", argv[0]); { char *nptr; n = strtol(argv[3], &nptr, 0); m = strtol(nptr+1, NULL, 0); is_range = *nptr == '-'; if(!n || !m || (*nptr != '-' && *nptr != '/')) die("Couldn't parse pattern %s\n", argv[3]); } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ USAGE Dropping A Range Of Frames -------------------------- To drop a range of frames, specify the starting frame and the ending frame to drop, separated by a dash. The following command will drop frames 5 through 10 (base 1). $ ./decode_with_drops in.ivf out.i420 5-10 Dropping A Pattern Of Frames ---------------------------- To drop a pattern of frames, specify the number of frames to drop and the number of frames after which to repeat the pattern, separated by a forward-slash. The following command will drop 3 of 7 frames. Specifically, it will decode 4 frames, then drop 3 frames, and then repeat. $ ./decode_with_drops in.ivf out.i420 3/7 Extra Variables --------------- This example maintains the pattern passed on the command line in the `n`, `m`, and `is_range` variables: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_VARS int n, m, is_range; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_VARS Making The Drop Decision ------------------------ The example decides whether to drop the frame based on the current frame number, immediately before decoding the frame. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE if((is_range && frame_cnt >= n && frame_cnt <= m) ||(!is_range && m - (frame_cnt-1)%m <= n)) { putc('X', stdout); continue; } putc('.', stdout); fflush(stdout); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE