This question is half StackOverflow and half SuperUser
I need information about simple and lossless video-only codecs that works in avconv. The purpose is to let screencap[1] produce one file for the entire sequence instead of one file per frame. The most straight-forward way is to write an MNG-VLC file instead of tons of PNG:s. However, no one seems to support that format, so I wonder if avconv does.
Requirements of the codec:
Easy to implement
Lossless
Decoding supported by avconv
Compression speed is a priority over file size
RGB-24 should be a supported pixel format
No inter-frame differencing (That makes multi-threading harder)
Not covered by any weird patents
If the question is to broad, it is good to get some clues where to start. I do not request a tool or library but technical information on the complexity of say ffv1.
[1] https://github.com/milasudril/screencap
I'm studying programming and in many sources I see the concepts: "machine language", "binary code" and "binary file". The distinction between these three is unclear to me, because according to my understanding machine language means the raw language that a computer can understand i.e. sequences of 0s and 1s.
Now if machine language is a sequence of 0s and 1s and binary code is also a sequence of 0s and 1s then does machine language = binary code?
What about binary file? What really is a binary file? To me the word "binary file" means a file, which consists of binary code. So for example, if my file was:
010010101010010
010010100110100
010101100111010
010101010101011
010101010100101
010101010010111
Would this be a binary file? If I google binary file and see Wikipedia I see this example picture of binary file which confuses me (it's not in binary?....)
Where is my confusion happening? Am I mixing file encoding here or what? If I were to ask one to SHOW me what is machine language, binary code and binary file, what would they be? =) I guess the distinction is too abstract to me.
Thnx for any help! =)
UPDATE:
In Python for example, there is one phrase in a file I/O tutorial, which I don't understand: Opens a file for reading only in binary format. What does reading a file in binary format mean?
Machine code and binary are the same - a number system with base 2 - either a 1 or 0. But machine code can also be expressed in hex-format (hexadecimal) - a number system with base 16. The binary system and hex are very interrelated with each other, its easy to convert from binary to hex and convert back from hex to binary. And because hex is much more readable and useful than binary - it's often used and shown. For instance in the picture above in your question -uses hex-numbers!
Let say you have the binary sequence 1001111000001010 - it can easily be converted to hex by grouping in blocks - each block consisting of four bits.
1001 1110 0000 1010 => 9 14 0 10 which in hex becomes: 9E0A.
One can agree that 9E0A is much more readable than the binary - and hex is what you see in the image.
I'm honestly surprised to not see the information I was looking for, looking back though, I guess the title of this thread isn't fully appropriate to the question the OP was asking.
You guys all say "Machine Code is a bunch of numbers".
Sure, the "CODE" is a bunch of numbers, but what people are wondering (I'm guessing) is "what actually is happening physically?"
I'm quite a novice when it comes to programming, but I understand enough to feel confident in 'roughly' answering this question.
Machine code, to the actual circuitry, isn't numbers or values.
Machine code is a bunch of voltage gates that are either open or closed, and depending on what they're connected to, a certain light will flicker at a certain time etc.
I'm guessing that the "machine code" dictates the pathway and timing for specific electrical signals that will travel to reach their overall destination.
So for 010101, 3 voltage gates are closed (The 0's), 3 are open (The 1's)
I know I'm close to the right answer here, but I also know it's much more sophisticated - because I can imagine that which I don't know.
010101 would be easy instructions for a simple circuit, but what I can't begin to fathom is how a complex computer processes all of the information.
So I guess let's break it down?
x-Bit-processors tell how many bits the processor can process at once.
A bit is either 1 or 0, "On" or "Off", "Open" or "Closed"
so 32-bit processors process "10101010 10101010 10101010 10101010" - this many bits at once.
A processor is an "integrated circuit", which is like a compact circuit board, containing resistors/capacitors/transistors and some memory. I'm not sure if processors have resistors but I know you'll usually find a ton of them located around the actual processor on the circuit board
Anyways, a transistor is a switch so if it receives a 1, it sends current in one direction, or if it receives a 0, it'll send current in a different direction... (or something like that)
So I imagine that as machine code goes... the segment of code the processor receives changes the voltage channels in such a way that it sends a signal to another part of the computer (why do you think processors have so many pins?), probably another integrated circuit more specialized to a specific task.
That integrated circuit then receives a chunk of code, let's say 2 to 4 bits 01 or 1100 or something, which further defines where the final destination of the signal will end up, which might be straight back to the processor, or possibly to some output device.
Machine code is a very efficient way of taking a circuit and connecting it to a lightbulb, and then taking that lightbulb out of the circuit and switching the circuit over to a different lightbulb
Memory in a computer is highly necessary because otherwise to get your computer to do anything, you would need to type out everything (in machine code). Instead, all of the 1's and 0's are stored inside some storage device, either a spinning hard disk with a magnetic head pin that 'reads' 1's or 0's based on the charge of the disk, or a flash memory device that uses a series of transistors, where sending a voltage through elicits 1's and 0's (I'm not fully aware how flash memory works)
Fortunately, someone took the time to think up a different base number system for programming (hex), and a way to compile those numbers (translate them) back into binary. And then all software programs have branched out from there.
Each key on the keyboard creates a specific signal in binary that translates to
a bunch of switches being turned on or off using certain voltages, so that a current could be run through the specific individual pixels on your screen that create "1" or "0" or "F", or all the characters of this post.
So I wonder, how does a program 'program', or 'make' the computer 'do' something... Rather, how does a compiler compile a program of a code different from binary?
It's hard to think about now because I'm extremely tired (so I won't try) but also because EVERYTHING you do on a computer is because of some program.
There are actively running programs (processes) in task manager. These keep your computer screen looking the way you've become accustomed, and also allow for the screen to be manipulated as if to say the pictures on the screen were real-life objects. (They aren't, they're just pictures, even your mouse cursor)
(Ok I'm done. enough editing and elongating my thoughts, it's time for bed)
Also, what I don't really get is how 0's are 'read' by the computer.
It seems that a '0' must not be a 'lack of voltage', rather, it must be some other type of signal
Where perhaps something like 1 volt = 1, and 0.5 volts = 0. Some distinguishable difference between currents in a circuit that would still send a signal, but could be the difference between opening and closing a specific circuit.
If I'm close to right about any of this, serious props to the computer engineers of the world, the level of sophistication is mouthwatering. I hope to know everything about technology someday. For now I'm just trying to get through arduino.
Lastly... something I've wondered about... would it even be possible to program today's computers without the use of another computer?
Machine language is a low-level programming language that generally consists entirely of numbers. Because they are just numbers, they can be viewed in binary, octal, decimal, hexadecimal, or any other way. Dave4723 gave a more thorough explanation in his answer.
Binary code isn't a very well-defined technical term, but it could mean any information represented by a sequence of 1s and 0s, or it could mean code in a machine language, or it could mean something else depending on context.
Technically, all files are stored in binary, we just don't usually look at the binary when we view a file. However, the term binary file is usually used to refer to any non-text file; e.g. an .exe, a .png, etc.
You have to understand how a computer works in its basic principles and this will clear things up for you... Therefore I recommend on reading into stuff like Neumann Architecture
Basically in a very simple computer you only have one memory like an array
which has instructions for your processor, the data and everything is a binary numbers.
Your program starts at a certain place in your memory and reads the first number...
so here comes the twist: these numbers can be instructions or data.
Your processor reads these numbers and interprets them as instructions
Example: the start address is 0
in 0 is a instruction like "read value from address 120 into the ALU (Math-Unit)
then it steps to address 1
"read value from address 121 into ALU"
then it steps to address 2
"subtract numbers in ALU"
then it steps to address 3
"if ALU-Value is smaller than zero go to address 10"
it is not smaller than zero so it steps to address 4
"go to address 20"
you see that this is a basic if(a < b)
You can write these instructions as numbers and they can be run by your processor but because nobody wants to do this work (that was what they did with punchcards in the 60s)
assembler was invented...
that looks like:
add 10 ,11, 20 // load var from address 10 and 11; run addition and store into address 20
In Conclusion:
Assembler (processor instructions) can be called binary because it's stored in plain numbers
But everything else can be a Binary file, too.
In reality if you have a simple .exe file it is both... If you have variables in there like a = 10 and b = 20, these values can be stored some where between if clauses and for loops... It depends on the compiler where it put these
But if you have a complex 3D-model it can be stored in a separate file with no executable code in it...
I hope it helps to clear things up a little.
I have a loop where I use dd to copy a stream to a disk. I am using a larger blocksize using 'bs' in the entire process for speed reasons. However with one specific line I have to use 'ibs' and 'obs' because my 'seek' location is not a multiple of the 'bs' I use elsewhere.
My question is: Is there a way using dd or any other program/Perl module to write out a blocksize different from the one used to 'seek'?
dd if=/dev/ram1 of=/dev/sdb1 seek=2469396480 ibs=1048576 obs=1 count=1
As you can see above, while the raw data is read in a 1M block I have to write it out in 1 byte segments because I need to seek to a specific location based on a byte granularity. This makes the write 1/100th as fast.
Is there a workaround? Or is there a way to do this in Perl without using dd?
Thanks,
Nick
This problem is inherent in dd. If your desired seek location has no factor of suitable magnitude (big enough for good performance but small enough to use as a buffer size) then you're stuck. This happens among other times when your desired seek location is a large prime.
In this specific case, as Mark Mann pointed out, you do have good options: 2469396480 is 2355 blocks of size 1048576, or 1024 blocks of size 2411520, etc... But that's not a generic answer.
To do this generically, you'll want to use something other than dd. Fortunately, dd's task is really simple and all you need is the following (in pseudocode... I haven't done much Perl in a while)
if = open("/dev/ram1", "r")
of = open("/dev/sdb1", "r+")
seek(of, 2469396480)
loop until you have copied the amount of data you want {
chunk = read(if, min(chunksize, remaining_bytes_to_copy))
write(of, chunk)
}
It looks like the source of your copy is a ramdisk of some sort. If you really want screaming performance, you might try another method besides reading chunks into a buffer and writing the buffer out to the output file. For example you can mmap() the source file and write() directly from the mapped address. The OS may (or may not) optimize away one of the RAM-to-RAM copy operations. Note that such methods will be less portable and less likely to be available in high level languages like Perl.
I am writing a small sniffer as part of a personal project. I am using Net::Pcap (really really great tool).
In the packet-processing loop I am using the excellent Net::Frame for unpacking all the headers and getting at the data. I am getting concerned that this might not be terribly efficient (Net::Frame is great but seems to be more than I need for this project).
Also I dislike that for some Debian systems I had to manually compile libdumbnet (the package provided in the official apt repositories didn't seem to work, Net-Libdnet-0.92 didn't like it).
All I want is to get at the payload inside a TCP segment. Is there any alternative ?
Thank you.
P.S. Would it be really really bad (read "thedailywtf.com worthy") if I just took the packet and searched it for some pattern ?
I recently wrote a PCAP dump file unpacker in C and then afterwards wished I'd just used the open source libraries instead (when I realised they existed and were so easy to use). I have to say that as it's a binary file format it's probably easier to do in C than Perl, but I'll no doubt get boo'ed by all the Perl fanatics out there.
What I will say is that using existing code will be quicker all round than coding it yourself, but if you really really want to, the file format is freely available online and is really quite simple.
As for searching for a pattern, it almost certainly won't work. It's a binary file format and the packets can be fragmented and/or duplicated, so the only reliable way to know where a message starts and ends is by unpacking the headers, checking the packet flags, reading the content length field, etc. etc. Doing pattern searches may work 90% of the time, but at some point you'll find a packet capture log that means you need to change your code. And then a while later find another packet that means another change, and so on and so forth.
What's a reliable way to automatically count the characters and/or words in a .doc or .docx file?
The only real requirement is a reasonably accurate and reasonably reliable count.
It needs to work with documents containing something other than Latin script, so counting characters is good enough for most cases.
The count does not necessarily need to match Word's, but the closer the better.
Since there are a gazillion different apps that can generate .doc files, it's okay to fail to count anything, but this case needs to be catchable so we're aware that a count may be inaccurate. For all other cases the count must be, say, at least 99% accurate at least 99% of the time.
I'm open as to the involved technologies, but something that can run on a *NIX command line would be greatly preferred.
Is there a reasonable solution for this?
Here's a link to some Linux word-to-text converters.
For example you could use
antiword file.doc | wc
to do the counting.
Edit:
This link shows that AbiWord has a command-line interface, that you could use to convert the .docx format to .txt and then count the words using "wc". AbiWord does support the docx format
Mac OS X has support for reading word files built into the system frameworks, so if you have that, it's easy. MacRuby sample:
NSSpellChecker.sharedSpellChecker.countWordsInString(NSAttributedString.alloc.initWithURL(fileURL, documentAttributes:nil), language:nil)
More portably — though it gives up support for docx — you could simply get Antiword and do antiword | wc -w.
Microsoft has published a specification for the Office binary file formats. Parsing a .DOC file doesn't look trivial, but with some care you should be able to get a dependable, repeatable result. I have no idea how closely it'll match with what Word shows -- that will probably depend (at least partly) on how you define "word" -- for example, whether you consider a group of digits a "word" or not. It probably won't take a lot to figure out how Word treats cases like that, so getting a close match shouldn't be terribly difficult.
If you consider online applications as a solution, yes, there is a solution.
This not so pretty (regarding the design) site offers both word and character count: http://allworldphone.com/count-words-characters.htm
I don't think there is a limit, and it shouldn't be a problem to just copy/paste the contents of your documents into the corresponding textarea and see the result.
Regarding the 100% or 99% accuracy, you could test it with a few (i.e. 20-50 words) by counting them yourself first.
I hope this helps.
Regards. Chris