我正在尝试为STL字幕格式（FFmpeg）编写一个demuxer。我很难理解ffmpeg中如何引用探测函数。
我的探测器有以下代码：
#include "avformat.h"
#include "internal.h"
#include "subtitles.h"
#include "libavutil/intreadwrite.h"
typedef struct {
FFDemuxSubtitlesQueue q;
} STLContext;
static int stl_probe(AVProbeData *p)
{
char c;
const unsigned char *ptr = p->buf;
av_log(0,100,"printing the probe function");
while(*ptr=='\r' || *ptr=='\n' || *ptr=='$' || (ptr[0]=='/' && ptr[1]=='/'))
ptr+=ff_subtitles_next_line(ptr);
if (sscanf(ptr, "%*d:%*d:%*d:%*d , %*d:%*d:%*d:%*d , %c", &c) == 1)
return AVPROBE_SCORE_MAX;
return 0;
}
static int64_t get_pts(char **buf, int *duration)
{
int hh1, mm1, ss1, ms1;
int hh2, mm2, ss2, ms2;
int len=0;
if (sscanf(*buf, "%2d:%2d:%2d:%2d , %2d:%2d:%2d:%2d , %n",
&hh1, &mm1, &ss1, &ms1,
&hh2, &mm2, &ss2, &ms2, &len) >= 8 && len>0) {
int64_t start = (hh1*3600LL + mm1*60LL + ss1) * 100LL + ms1;
int64_t end = (hh2*3600LL + mm2*60LL + ss2) * 100LL + ms2;
*duration = end - start;
*buf+=len;
return start;
}
return AV_NOPTS_VALUE;
}
static int stl_read_header(AVFormatContext *s)
{
STLContext *stl = s->priv_data;
AVStream *st = avformat_new_stream(s, NULL);
if (!st)
return AVERROR(ENOMEM);
avpriv_set_pts_info(st, 64, 1, 100);
st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
st->codec->codec_id = AV_CODEC_ID_TEXT;
while (!avio_feof(s->pb)) {
char line[4096];
char *p = line;
const int64_t pos = avio_tell(s->pb);
int len = ff_get_line(s->pb, line, sizeof(line));
int64_t pts_start;
int duration;
if (!len)
break;
line[strcspn(line, "\r\n")] = 0;
pts_start = get_pts(&p , &duration);
if (pts_start != AV_NOPTS_VALUE) {
AVPacket *sub;
sub = ff_subtitles_queue_insert(&stl->q, p, strlen(p), 0);
if (!sub)
return AVERROR(ENOMEM);
sub->pos = pos;
sub->pts = pts_start;
sub->duration = duration;
}
}
ff_subtitles_queue_finalize(&stl->q);
return 0;
}
static int stl_read_packet(AVFormatContext *s, AVPacket *pkt)
{
STLContext *stl = s->priv_data;
return ff_subtitles_queue_read_packet(&stl->q, pkt);
}
static int stl_read_seek(AVFormatContext *s, int stream_index,
int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
{
STLContext *stl = s->priv_data;
return ff_subtitles_queue_seek(&stl->q, s, stream_index,
min_ts, ts, max_ts, flags);
}
static int stl_read_close(AVFormatContext *s)
{
STLContext *stl = s->priv_data;
ff_subtitles_queue_clean(&stl->q);
return 0;
}
AVInputFormat ff_stl_demuxer = {
.name = "stl",
.long_name = NULL_IF_CONFIG_SMALL("STL subtitles"),
.priv_data_size = sizeof(STLContext),
.read_probe = stl_probe,
.read_header = stl_read_header,
.read_packet = stl_read_packet,
.read_seek2 = stl_read_seek,
.read_close = stl_read_close,
.extensions = "stl",
};
./ffmpeg -f stl -i Test.stl Test.srt的输出ffmpeg version N-66838-g9071bab Copyright (c) 2000-2014 the FFmpeg developers
built on Oct 14 2014 12:28:54 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
configuration:
libavutil 54. 10.100 / 54. 10.100
libavcodec 56. 4.101 / 56. 4.101
libavformat 56. 9.100 / 56. 9.100
libavdevice 56. 1.100 / 56. 1.100
libavfilter 5. 1.105 / 5. 1.105
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
Input #0, stl, from '/home/eejya/SubtitleTesting/UK_FINAL_240511.stl':
Duration: N/A, bitrate: N/A
Stream #0:0: Subtitle: text
Output #0, srt, to '/home/eejya/SubtitleTesting/UkTest.srt':
Metadata:
encoder : Lavf56.9.100
Stream #0:0: Subtitle: subrip (srt)
Metadata:
encoder : Lavc56.4.101 srt
Stream mapping:
Stream #0:0 -> #0:0 (text (native) -> subrip (srt))
Press [q] to stop, [?] for help
size= 10kB time=00:27:10.06 bitrate= 0.0kbits/s
video:0kB audio:0kB subtitle:4kB other streams:0kB global headers:0kB muxing overhead: 121.594238%
当我运行命令时
./ffmpeg -i Test.stl Test.srt
我没有看到av_log打印的任何输出，它显示探针得分非常低，这可能导致错误检测。这意味着只检查扩展名。因此，要么没有调用我的探测函数，要么没有读取缓冲区。
如何检查是否调用了探测函数？
低分警告是否意味着正在调用函数？
最佳答案
我在本地编译并测试了您所做的更改。您的STL demuxer已注册：
$ ./ffmpeg -formats
...
D stl STL subtitles
...
正在调用探测函数，并正在使用STL demuxer。但是，您没有看到打印任何日志条目，因为：
av_log(0, 100, "printing the probe function");
^ ^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| | |
| | message
| |
| log level
|
context
你的日志级别是100。In FFmpeg, a higher log level means a less severe message, and by default FFmpeg only prints messages of
AV_LOG_INFO (32) level or lower。如果将函数调用更改为：av_log(NULL, AV_LOG_FATAL, "printing the probe function\n");
// AV_LOG_FATAL is 8
你会看到你的信息被打印出来。
关于c - ffmpeg中的探测功能，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/26363816/