FFMPEG转码时，kill一次有可能FFMPEG进程没法退出

FFMPEG 版本3.2 release

 

以前遇到过调用FFMPEG转码，kill一次没法中止转码过程。

做为一个记录，具体缘由未知，奇怪的问题。

 

转码过程调用函数transcode()

while (!received_sigterm) {
        int64_t cur_time= av_gettime_relative();

        /* if 'q' pressed, exits */
        if (stdin_interaction)
            if (check_keyboard_interaction(cur_time) < 0)
                break;

        /* check if there's any stream where output is still needed */
        if (!need_output()) {
            av_log(NULL, AV_LOG_VERBOSE, "No more output streams to write to, finishing.\n");
            break;
        }

        ret = transcode_step();
        if (ret < 0 && ret != AVERROR_EOF) {
            char errbuf[128];
            av_strerror(ret, errbuf, sizeof(errbuf));

            av_log(NULL, AV_LOG_ERROR, "Error while filtering: %s\n", errbuf);
            break;
        }

        /* dump report by using the output first video and audio streams */
        print_report(0, timer_start, cur_time);
  }

received_sigterm变量的值

static volatile int received_sigterm = 0;
static volatile int received_nb_signals = 0;
static volatile int transcode_init_done = 0;
static volatile int ffmpeg_exited = 0;
static int main_return_code = 0;

static void
sigterm_handler(int sig)
{
    received_sigterm = sig;
    received_nb_signals++;
    term_exit_sigsafe();
    if(received_nb_signals > 3) {
        write(2/*STDERR_FILENO*/, "Received > 3 system signals, hard exiting\n",
                           strlen("Received > 3 system signals, hard exiting\n"));

        exit(123);
    }
}

也就是说只要执行函数sigterm_handler()，received_sigterm的值确定不为0.

sigterm_handler()信号处理函数

void term_init(void)
{
#if HAVE_TERMIOS_H
    if (!run_as_daemon && stdin_interaction) {
        struct termios tty;
        if (tcgetattr (0, &tty) == 0) {
            oldtty = tty;
            restore_tty = 1;

            tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP
                             |INLCR|IGNCR|ICRNL|IXON);
            tty.c_oflag |= OPOST;
            tty.c_lflag &= ~(ECHO|ECHONL|ICANON|IEXTEN);
            tty.c_cflag &= ~(CSIZE|PARENB);
            tty.c_cflag |= CS8;
            tty.c_cc[VMIN] = 1;
            tty.c_cc[VTIME] = 0;

            tcsetattr (0, TCSANOW, &tty);
        }
        signal(SIGQUIT, sigterm_handler); /* Quit (POSIX).  */
    }
#endif

    signal(SIGINT , sigterm_handler); /* Interrupt (ANSI).    */
    signal(SIGTERM, sigterm_handler); /* Termination (ANSI).  */
#ifdef SIGXCPU
    signal(SIGXCPU, sigterm_handler);
#endif
#if HAVE_SETCONSOLECTRLHANDLER
    SetConsoleCtrlHandler((PHANDLER_ROUTINE) CtrlHandler, TRUE);
#endif
}

个人理解是，只要kill ffmpeg进程，那么确定会执行sigterm_handler()函数，也就是received_sigterm这个的值确定不为0，会中止转码。

可是事实有可能不是这样的，为何哪？