原来ffmpeg中的参数对应是这样的
#define OFFSET(x) offsetof(OptionsContext, x)
const OptionDef options[] = {
/* main options */
#include "cmdutils_common_opts.h"
{ "f", HAS_ARG | OPT_STRING | OPT_OFFSET |
OPT_INPUT | OPT_OUTPUT, { .off = OFFSET(format) },
"force format", "fmt" },
{ "y", OPT_BOOL, { &file_overwrite },
"overwrite output files" },
{ "n", OPT_BOOL, { &no_file_overwrite },
"never overwrite output files" },
{ "ignore_unknown", OPT_BOOL, { &ignore_unknown_streams },
"Ignore unknown stream types" },
{ "copy_unknown", OPT_BOOL | OPT_EXPERT, { ©_unknown_streams },
"Copy unknown stream types" },
{ "c", HAS_ARG | OPT_STRING | OPT_SPEC |
OPT_INPUT | OPT_OUTPUT, { .off = OFFSET(codec_names) },
"codec name", "codec" },
{ "codec", HAS_ARG | OPT_STRING | OPT_SPEC |
OPT_INPUT | OPT_OUTPUT, { .off = OFFSET(codec_names) },
"codec name", "codec" },
{ "pre", HAS_ARG | OPT_STRING | OPT_SPEC |
OPT_OUTPUT, { .off = OFFSET(presets) },
"preset name", "preset" },
{ "map", HAS_ARG | OPT_EXPERT | OPT_PERFILE |
OPT_OUTPUT, { .func_arg = opt_map },
"set input stream mapping",
"[-]input_file_id[:stream_specifier][,sync_file_id[:stream_specifier]]" },
{ "map_channel", HAS_ARG | OPT_EXPERT | OPT_PERFILE | OPT_OUTPUT, { .func_arg = opt_map_channel },
"map an audio channel from one stream to another", "file.stream.channel[:syncfile.syncstream]" },
{ "map_metadata", HAS_ARG | OPT_STRING | OPT_SPEC |
OPT_OUTPUT, { .off = OFFSET(metadata_map) },
"set metadata information of outfile from infile",
"outfile[,metadata]:infile[,metadata]" },
{ "map_chapters", HAS_ARG | OPT_INT | OPT_EXPERT | OPT_OFFSET |
OPT_OUTPUT, { .off = OFFSET(chapters_input_file) },
"set chapters mapping", "input_file_index" },
{ "t", HAS_ARG | OPT_TIME | OPT_OFFSET |
OPT_INPUT | OPT_OUTPUT, { .off = OFFSET(recording_time) },
"record or transcode \"duration\" seconds of audio/video",
"duration" },
{ "to", HAS_ARG | OPT_TIME | OPT_OFFSET | OPT_OUTPUT, { .off = OFFSET(stop_time) },
"record or transcode stop time", "time_stop" },
{ "fs", HAS_ARG | OPT_INT64 | OPT_OFFSET | OPT_OUTPUT, { .off = OFFSET(limit_filesize) },
"set the limit file size in bytes", "limit_size" },
{ "ss", HAS_ARG | OPT_TIME | OPT_OFFSET |
OPT_INPUT | OPT_OUTPUT, { .off = OFFSET(start_time) },
"set the start time offset", "time_off" },
{ "sseof", HAS_ARG | OPT_TIME | OPT_OFFSET |
OPT_INPUT | OPT_OUTPUT, { .off = OFFSET(start_time_eof) },
"set the start time offset relative to EOF", "time_off" },
{ "seek_timestamp", HAS_ARG | OPT_INT | OPT_OFFSET |
OPT_INPUT, { .off = OFFSET(seek_timestamp) },
"enable/disable seeking by timestamp with -ss" },
{ "accurate_seek", OPT_BOOL | OPT_OFFSET | OPT_EXPERT |
OPT_INPUT, { .off = OFFSET(accurate_seek) },
"enable/disable accurate seeking with -ss" },
{ "itsoffset", HAS_ARG | OPT_TIME | OPT_OFFSET |
OPT_EXPERT | OPT_INPUT, { .off = OFFSET(input_ts_offset) },
"set the input ts offset", "time_off" },
{ "itsscale", HAS_ARG | OPT_DOUBLE | OPT_SPEC |
OPT_EXPERT | OPT_INPUT, { .off = OFFSET(ts_scale) },
"set the input ts scale", "scale" },
{ "timestamp", HAS_ARG | OPT_PERFILE | OPT_OUTPUT, { .func_arg = opt_recording_timestamp },
"set the recording timestamp ('now' to set the current time)", "time" },
{ "metadata", HAS_ARG | OPT_STRING | OPT_SPEC | OPT_OUTPUT, { .off = OFFSET(metadata) },
"add metadata", "string=string" },
{ "program", HAS_ARG | OPT_STRING | OPT_SPEC | OPT_OUTPUT, { .off = OFFSET(program) },
"add program with specified streams", "title=string:st=number..." },
{ "dframes", HAS_ARG | OPT_PERFILE | OPT_EXPERT |
OPT_OUTPUT, { .func_arg = opt_data_frames },
"set the number of data frames to output", "number" },
{ "benchmark", OPT_BOOL | OPT_EXPERT, { &do_benchmark },
"add timings for benchmarking" },
{ "benchmark_all", OPT_BOOL | OPT_EXPERT, { &do_benchmark_all },
"add timings for each task" },
{ "progress", HAS_ARG | OPT_EXPERT, { .func_arg = opt_progress },
"write program-readable progress information", "url" },
{ "stdin", OPT_BOOL | OPT_EXPERT, { &stdin_interaction },
"enable or disable interaction on standard input" },
{ "timelimit", HAS_ARG | OPT_EXPERT, { .func_arg = opt_timelimit },
"set max runtime in seconds", "limit" },
{ "dump", OPT_BOOL | OPT_EXPERT, { &do_pkt_dump },
"dump each input packet" },
{ "hex", OPT_BOOL | OPT_EXPERT, { &do_hex_dump },
"when dumping packets, also dump the payload" },
<span style="color:#ff0000;"> { </span><span style="color:#cc33cc;">"re", </span><span style="color:#ff0000;"> OPT_BOOL | OPT_EXPERT | OPT_OFFSET |
OPT_INPUT, { .off = OFFSET(</span>rate_emu)<span style="color:#ff0000;"> }, //======说明参数 -re 对应 源码中的参数 rate_emu</span>
"read input at native frame rate", "" },
{ "target", HAS_ARG | OPT_PERFILE | OPT_OUTPUT, { .func_arg = opt_target },
"specify target file type (\"vcd\", \"svcd\", \"dvd\", \"dv\" or \"dv50\" "
"with optional prefixes \"pal-\", \"ntsc-\" or \"film-\")", "type" },
{ "vsync", HAS_ARG | OPT_EXPERT, { .func_arg = opt_vsync },
"video sync method", "" },
{ "frame_drop_threshold", HAS_ARG | OPT_FLOAT | OPT_EXPERT, { &frame_drop_threshold },
"frame drop threshold", "" },
。。。。。
};
---- rate_emu Matches (7 in 3 files) ----
Ffmpeg.c: if (ifile->rate_emu)
Ffmpeg.c: if (f->rate_emu) {
Ffmpeg.h: int rate_emu;
Ffmpeg.h: int rate_emu;
Ffmpeg_opt.c: f->rate_emu = o->rate_emu;
Ffmpeg_opt.c: OPT_INPUT, { .off = OFFSET(rate_emu) },
再相应的找对应代码就OK了
主要代码是
static int get_input_packet(InputFile *f, AVPacket *pkt)
{
if (f->rate_emu) {
int i;
for (i = 0; i < f->nb_streams; i++) {
InputStream *ist = input_streams[f->ist_index + i];
int64_t pts = av_rescale(ist->dts, 1000000, AV_TIME_BASE);
int64_t now = av_gettime_relative() - ist->start;
if (pts > now)
return AVERROR(EAGAIN);
}
}
#if HAVE_PTHREADS
if (nb_input_files > 1)
return get_input_packet_mt(f, pkt);
#endif
return av_read_frame(f->ctx, pkt);
}
//也就是说控制读取数据来控制的速度