一、為什么想到這個問題
昨天在電腦上看視頻的時候，發現字幕有些問題。具體的問題就是視頻是分兩個文件的，但是字幕是單個文件的，所以在看第二個文件的時候字幕就對不上了，而且相差很大，這個時候就需要手動對齊字幕，這個誤差大概是50分鍾，也就是3K秒左右，播放器貌似又不支持直接設置一個偏移量，所以我就只能通過按鍵手動對齊，每次按鍵調整1秒的偏差。按下之后就體會到了長按自動重復的好處，只要按着不松手，播放器就會自動的發送按鍵事件。我搜索了下怎么樣讓這個按鍵生成的速度更快一些，找到了windows下
修改這配置的說明，因為作者的描述比較形象，例如作者說的“字符像機關槍的子彈一樣射到屏幕上”這個生動的描述，感覺作者的腦洞開的有點大，並且也是個性情中人。我就把作者的描述搬過來了
Repeat delay: When you press and hold a key on a computer keyboard, the key eventually repeats itself, spewing out characters across the screen like bullets from a machine gun. The pause between pressing the key and when it starts repeating is the repeat delay.
Repeat rate: After you press and hold down a key on the keyboard, the key starts repeating itself. The speed at which it repeats is the repeat rate, which can be fast or slow.
對於win7的設置路徑
系統左下角的“開始”按鈕===>“設備與打印機”>===>>"USB NetVista Full WIdth Keyboard"右鍵===>>鍵盤設置===>>速度===>>字符重復
重復速度 重復延遲
設置之后效果非常明顯，這樣對齊字幕的時候就快很多了。
二、這個重復是誰做的
因為最近剛好在看gui相關內容，就考慮了下是誰執行的重復，是windows explorer、操作系統還是說是硬件執行的？好在開源的linux提供了類似的功能，最為直觀的對應就是kbdrate，圖形界面的xset也有相同功能，但是它的結構比較復雜，所以還是看命令行的kbdrate，這個基本就可以確定是軟件還是硬件來實現。
tsecer@harry: strace kbdrate 2>&1| grep io
ioctl(0, KDKBDREP, 0xbf95d210) = -1 EINVAL (Invalid argument)
rt_sigaction(SIGALRM, {0x8048f30, [ALRM], SA_RESTART}, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
tsecer@harry:
操作系統中對於這個命令的處理相關為
#define KDKBDREP 0x4B52 /* set keyboard delay/repeat rate;
* actually used values are returned */
#define ATKBD_CMD_SETREP 0x10
f3
linux-3.12.6\drivers\input\keyboard\atkbd.c
static int atkbd_set_repeat_rate(struct atkbd *atkbd)
{
const short period[32] =
{ 33, 37, 42, 46, 50, 54, 58, 63, 67, 75, 83, 92, 100, 109, 116, 125,
133, 149, 167, 182, 200, 217, 232, 250, 270, 303, 333, 370, 400, 435, 470, 500 };
const short delay[4] =
{ 250, 500, 750, 1000 };
struct input_dev *dev = atkbd->dev;
unsigned char param;
int i = 0, j = 0;
while (i < ARRAY_SIZE(period) - 1 && period[i] < dev->rep[REP_PERIOD])
i++;
dev->rep[REP_PERIOD] = period[i];
while (j < ARRAY_SIZE(delay) - 1 && delay[j] < dev->rep[REP_DELAY])
j++;
dev->rep[REP_DELAY] = delay[j];
param = i | (j << 5);
return ps2_command(&atkbd->ps2dev, ¶m, ATKBD_CMD_SETREP);
}
三、這個重復可以有多快
kbdrate的man手冊中說明
OPTIONS
-s Silent. No messages are printed.
-r rate
Change the keyboard repeat rate to rate cps. For Intel-based
systems, the allowable range is from 2.0 to 30.0 cps. Only cer-
tain, specific values are possible, and the program will select
the nearest possible value to the one specified. The possible
values are given, in characters per second, as follows: 2.0,
2.1, 2.3, 2.5, 2.7, 3.0, 3.3, 3.7, 4.0, 4.3, 4.6, 5.0, 5.5, 6.0,
6.7, 7.5, 8.0, 8.6, 9.2, 10.0, 10.9, 12.0, 13.3, 15.0, 16.0,
17.1, 18.5, 20.0, 21.8, 24.0, 26.7, 30.0. For SPARC-based sys-
tems, the allowable range is from 0 (no repeat) to 50 cps.
-d delay
Change the delay to delay milliseconds. For Intel-based sys-
tems, the allowable range is from 250 to 1000 ms, in 250 ms
steps. For SPARC systems, possible values are between 10 ms and
1440 ms, in 10 ms steps.
從前面內核中的代碼來看，它有這樣的一組對應的數字
const short period[32] =
{ 33, 37, 42, 46, 50, 54, 58, 63, 67, 75, 83, 92, 100, 109, 116, 125,
133, 149, 167, 182, 200, 217, 232, 250, 270, 303, 333, 370, 400, 435, 470, 500 };
可以看到這個順序是和man手冊中 -r rate說明的數字相對應，並且剛好順序相反，兩者的乘積大概是1000。這里也說明了重復按鍵的最大頻率，也就是1秒鍾最多重復30次。以需要同步50分鍾為例，秒鍾最多重復30次，所以字幕同步時間大概為50*60/30=100秒。
四、關於鍵盤驅動中的命令說明
由於這個筆記比較短，而
這個文檔挺重要的，我就多搬了點過來：
Below are all the commands the host may send to the keyboard:
Repeat Rate
- 0xFF (Reset) - Keyboard responds with "ack" (0xFA), then enters "Reset" mode. (See "Reset" section.)
- 0xFE (Resend) - Keyboard responds by resending the last-sent byte. The exception to this is if the last-sent byte was "resend" (0xFE). If this is the case, the keyboard resends the last non-0xFE byte. This command is used by the host to indicate an error in reception.
The next six commands can be issued when the keyboard is in any mode, but it only effects the behavior of the keyboard when in "mode 3" (ie, set to scan code set 3.)
- *0xFD (Set Key Type Make) - Disable break codes and typematic repeat for specified keys. Keyboard responds with "ack" (0xFA), then disables scanning (if enabled) and reads a list of keys from the host. These keys are specified by their set 3 make codes. Keyboard responds to each make code with "ack". Host terminates this list by sending an invalid set 3 make code (eg, a valid command.) The keyboard then re-enables scanning (if previously disabled).
- *0xFC (Set Key Type Make/Break) - Similar to previous command, except this one only disables typematic repeat.
- *0xFB (Set Key Type Typematic) - Similar to previous two, except this one only disables break codes.
- *0xFA (Set All Keys Typematic/Make/Break) - Keyboard responds with "ack" (0xFA). Sets all keys to their normal setting (generate scan codes on make, break, and typematic repeat)
- *0xF9 (Set All Keys Make) - Keyboard responds with "ack" (0xFA). Similar to 0xFD, except applies to all keys.
- *0xF8 (Set All Keys Make/Break) - Keyboard responds with "ack" (0xFA). Similar to 0xFC, except applies to all keys.
- *0xF7 (Set All Keys Typematic) - Keyboard responds with "ack" (0xFA). Similar to 0xFB, except applies to all keys.
- 0xF6 (Set Default) - Load default typematic rate/delay (10.9cps / 500ms), key types (all keys typematic/make/break), and scan code set (2).
- 0xF5 (Disable) - Keyboard stops scanning, loads default values (see "Set Default" command), and waits further instructions.
- 0xF4 (Enable) - Re-enables keyboard after disabled using previous command.
- 0xF3 (Set Typematic Rate/Delay) - Host follows this command with one argument byte that defines the typematic rate and delay as follows:
-
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2.0 |
Delay
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- *0xF2 (Read ID) - The keyboard responds by sending a two-byte device ID of 0xAB, 0x83. (0xAB is sent first, followed by 0x83.)
- *0xF0 (Set Scan Code Set) - Keyboard responds with "ack", then reads argument byte from the host. This argument byte may be 0x01, 0x02, or 0x03 to select scan code set 1, 2, or 3, respectively. The keyboard responds to this argument byte with "ack". If the argument byte is 0x00, the keyboard responds with "ack" followed by the current scan code set.
- 0xEE (Echo) - The keyboard responds with "Echo" (0xEE).
- 0xED (Set/Reset LEDs) - The host follows this command with one argument byte, that specifies the state of the keyboard's Num Lock, Caps Lock, and Scroll Lock LEDs. This argument byte is defined as follows:
| MSb | LSb |
| Always 0 | Always 0 | Always 0 | Always 0 | Always 0 | Caps Lock | Num Lock | Scroll Lock |
*Originally available in PS/2 keyboards only.
- "Scroll Lock" - Scroll Lock LED off(0)/on(1)
- "Num Lock" - Num Lock LED off(0)/on(1)
- "Caps Lock" - Caps Lock LED off(0)/on(1)