# Tag: simultaneously

## 7.0 nougat – Playing two videos/audios simultaneously in twin view

In short: is there any way to watch (and hear) simultaneously two stream sources?

Here some details.

I’m using a Samsung Galazy tab S2 with Android 7.

I have noticed that if I open in twin view

multiple window applications playing videos I can watch them simultaneously as long as only one window is using the audio.

Once I try to play the other video’s audio

the first video is stopped.

Is there any way to avoid this block?

Thanks in advance for any answer.

## help solving 3 algebraic statements simultaneously

i have three algebraic expressions, each using the others. in these equations `a`

, `b`

, `c`

and `t`

are known and plugged in later:

$x = a^{-1}(t + y + z)$

$y = b^{-1}(t + x + z)$

$z = c^{-1}(t + x + y)$

i have managed to successfully solve the equations for two statements using substitution:

$x = a^{-1}(t + y)$

$y = b^{-1}(t + x)$

which substitutes and simplifies as:

$x = a^{-1}t + a^{-1}b^{-1}t + a^{-1}b^{-1}x$

$x – a^{-1}b^{-1}x = a^{-1}t + a^{-1}b^{-1}t$

$x(1 – a^{-1}b^{-1}) = a^{-1}t(b^{-1} + 1)$

therefore:

$x = a^{-1}t(1+b^{-1}) / (1 – a^{-1}b^{-1})$

$y = b^{-1}t(1+a^{-1}) / (1 – a^{-1}b^{-1})$

but introducing a third term has me stumped, as i keep getting a nonsense result when substituting leaving me with $x = x$ when i simplify the equation. (this is obviously correct, but also useless.) I’m hoping that someone would be so kind as to explain how i go about substituting more than one term and solving `x`

, `y`

and `z`

in terms of `t`

, `a`

, `b`

and `c`

. does the same principle apply as with two terms?

for completeness, here is my (incorrect) work:

$x = a^{-1}t + a^{-1}y + a^{-1}z$

$a^{-1}z = x – (a^{-1}t + a^{-1}y)$

$a^{-1}z = x – a^{-1}(t + y)$

$z = ax – (t + y)$ `(multiply both sides by a)`

therefore, to find `y`

i substitute `z`

:

$x = a^{-1}t + a^{-1}y + a^{-1}(ax – (t + y))$

$x = a^{-1}t + a^{-1}y + x – a^{-1}t – a^{-1}y$

$x = (a^{-1}t – a^{-1}t) + (a^{-1}y – a^{-1}y) + x$

$x = 0 + 0 + x$

$x = x$

please forgive me if my terminology isn’t correct. i don’t exactly have a maths background and english isn’t my first language.

## Is my iPod Touch 2G supposed to be outputting audio over headphones and internal speaker simultaneously?

I know this is an old device but I hope it’s still okay to ask about it.

I got a 2nd gen (I think) 8GB iPod Touch from my partner last week. She forgot the pin so I just restored it in iTunes.

I loaded some of my music onto it and noticed today that the music was also playing from the internal speaker, *as well as* my headphones. Is this normal, or expected, behaviour for this device? It looks to be in great shape hardware wise (no external damage apart from the standard scratching of the back) and I haven’t jailbroken it.

## How do I simultaneously update unique keys in PostgreSQL?

```
CREATE TABLE widget (
id serial PRIMARY KEY,
name text NOT NULL,
ordinal int NOT NULL UNIQUE
);
```

I have the data

```
id | name | ordinal
----+------+---------
1 | A | 1
2 | B | 2
3 | C | 3
```

I would like to update it to

```
id | name | ordinal
----+------+---------
1 | A | 3
2 | B | 2
3 | C | 1
```

Touching records as little as possible (i.e. don’t rewrite the entire record set, don’t kick off unnecessary triggers), what’s the generally applicable approach to updating `ordinal`

to be the target values?

A vanilla update just gives me constraint violations, even if it happens in a single statement.

And dropping and recreating the unique constraint is expensive and poor concurrency.

This seems like a common enough problem that there ought to be a good way to do this, that I just can’t think of.

## operating systems – Starvation and Livelock simultaneously

Doubt: In the mentioned scheme, Can any process suffer from Starvation?

My thoughts:

My understanding, Starvation is waiting indefinitely for the resource or to get scheduled etc. (A/c to Galvin Book). So, here in this question, Any process needing any resource at any point can call the OWNRESOURCE function and process will surely get the resource it asked for. So, we can surely say that the process doesn’t have to wait indefinitely at any point. Hence we don’t have Starvation.

Problem? I have read that Livelock is a special kind of Starvation(Resource Starvation), Clearly the Scheme mentioned in the question suffers from Livelock. But it can’t possibly suffer from Starvation.

Note: I have asked similar question(deleted now) but didn’t expressed my thoughts well and didn’t have any discussion. Now, I’m very specific about my doubts and I have articulated my thoughts as well.

## Mathematica shorthand for mapping function over two lists simultaneously

If `phif`

and `phit`

are not lists, then MassDefect’s and ciao’s suggestions in comments as well as variations of them work:

```
ClearAll(v1, v2, a, b, phif, x)
v1 = Array(a, 3);
v2 = Array(b, 3);
phif = x;
result1 = Table(findcvec(phif, phit, v1((i)), v2((i)), +1), {i, Length(v1)})
```

`{findcvec(phif, phit, a(1), b(1), 1), findcvec(phif, phit, a(2), b(2), 1), findcvec(phif, phit, a(3), b(3), 1)}`

```
result2 = MapThread(findcvec(phif, phit, #1, #2, 1) &, {v1, v2});
(* MassDefect's comment *)
result3 = Thread(findcvec(phif, phit, #1, #2, 1)) & @@ {v1, v2};
(* ciao's comment *)
result2b = MapThread(findcvec(phif, phit, #1, #2, 1) &)@{v1, v2};
result3b = Thread(findcvec(phif, phit, #1, #2, 1) & @@ {v1, v2});
result3c = Thread(findcvec(phif, phit, v1, v2, 1));
result4 = Inner(findcvec(phif, phit, #1, #2, 1) &, v1, v2, List);
result1 == result2 == result2b == result3 == result3b == result3c == result4
```

`True`

If either of `phif`

and `phit`

(say, `phif`

) is a list then we need to modify the methods with `Thread`

to use second and third arguments to specify what to thread on:

```
phif = {x, y, z};
result1 = Table(findcvec(phif, phit, v1((i)), v2((i)), +1), {i, Length(v1)})
```

`{findcvec({x, y, z}, phit, a(1), b(1), 1), findcvec({x, y, z}, phit, a(2), b(2), 1), findcvec({x, y, z}, phit, a(3), b(3), 1)}`

```
result2 = MapThread(findcvec(phif, phit, #1, #2, 1) &, {v1, v2});
(* MassDefect's comment *)
result3 = Thread(findcvec(phif, phit, #1, #2, 1), List, {3, 4}) & @@ {v1, v2};
(* ciao's comment *)
result2b = MapThread(findcvec(phif, phit, #1, #2, 1) &)@{v1, v2};
result3b = Thread(findcvec(phif, phit, #1, #2, 1) & @@ {v1, v2}, List, {3, 4});
result3c = Thread(findcvec(phif, phit, v1, v2, 1), List, {3, 4});
result4 = Inner(findcvec(phif, phit, #1, #2, 1) &, v1, v2, List);
result1 == result2 == result2b == result3 == result3b == result3c == result4
```

`True`

## wireless networking – Can 802.11 a/b/g/n adapter sniff a b g n traffic simultaneously in monitor mode?

I have wifi adapter based on rt5572 which supports a/b/g/n. And let’s say I have Mixed mode wifi network where there is AP and a, b, g, n wifi clients all in the same network.

The questions I have:

Question 1:

If I put my rt5572 wifi adapter into monitor mode and start sniffing 802.11 packets in the air, will I be able to see all management frames, control frames and data frames from a, b, g, n clients if my monitor mode adapter is in same channel as them?

Question 2:

If my wifi adapter in monitor mode can capture all a, b, g, n traffic in the same channel(including data traffic, not just management and control frames in legacy rate) from a, b, g, n wifi clients, how is this possible because a,g,n PHY layer technology is OFDM but 802.11b PHY layer technology is DSSS. Does my WiFi adapter detect modulation and decode a,b,g,n traffic accordingly even if 802.11b use different PHY modulation?

These are questions I have for long time since gotten into Kali and wifi sniffing.

## How can I use Tailscale with the Google Fi VPN simultaneously?

I use Tailscale to connect between my devices. It assigns IP addresses to my devices from the 100.64.0.0/10 address space, which is not publicly routable, since it is a private address space intended for CGNAT. I want to be able to connect to my devices on this pseudo-internal network as well as using the Google Fi VPN for all my other traffic. How can I make this happen?

In theory, it could be done with VPN daisy-chaining, but this is apparently not possible on Android. Can it be done if I am rooted, or is there any other way to do it?

## How to solve one quartic equation and one linear equation simultaneously?

How to solve one quartic equation and one linear equation simultaneously ?