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I'm looking for a way to make a USB device show up as if it has different vendor and product IDs. I'm trying to make a proprietary piece of software to work with a USB device that should be supported but gets rejected solely because of its ID.
The software is for Windows, but I can run it in a VM in Linux. So I'll be fine with either approach, whatever works:
Changing USB ID in Linux
Changing USB ID in Windows
Making Qemu (or perhaps some other equivalent) change USB ID in passthrough
There may be a simpler way to do this, but I was faced with a similar problem and was able to create a process in which I could change the device descriptor information for development purposes. The process is summarized in this diagram:
First configure a static IP address for you Raspberry Pi and configure your PC ethernet TCP/IPv4 settings so you are able to communicate with you Raspberry Pi over the LAN connection.
Download the Virtual Here Raspberry Pi server and the client software for your PC from the Virtual Here website. The trial version will work for this use case.
Move the Virtual Here server software to you Raspberry Pi. In order to run the USB server you need to change the privileges of the file with $ sudo chmod +x vhusbdarm then run with $ sudo ./vhusbdarm.
Run the client software on your local machine. You will see that the client detects the USB device on the USB device server at <Your Raspberry Pi IP address>:7575. Connecting to the device at this point will give no advantage and mimic a direct connection.
Run the python file bellow, which was modified from a solution I found here, but utilizes Scapy sniff to capture the incoming packets before forwarding the raw data. The original script in the linked solution should work fine as well. In the script you can see that I used port 12345.
#!/usr/bin/env python
from scapy.all import *
import socket
import threading
import select
from queue import Queue
main_queue = Queue()
terminateAll = False
class ClientThread(threading.Thread):
def __init__(self, clientSocket, targetHost, targetPort):
threading.Thread.__init__(self)
self.__clientSocket = clientSocket
self.__targetHost = targetHost
self.__targetPort = targetPort
def run(self):
print("Client Thread started")
self.__clientSocket.setblocking(0)
targetHostSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
targetHostSocket.connect((self.__targetHost, self.__targetPort))
targetHostSocket.setblocking(0)
clientData = b""
targetHostData = b""
terminate = False
while not terminate and not terminateAll:
inputs = [self.__clientSocket, targetHostSocket]
outputs = []
if len(clientData) > 0:
outputs.append(self.__clientSocket)
if len(targetHostData) > 0:
outputs.append(targetHostSocket)
try:
inputsReady, outputsReady, errorsReady = select.select(inputs, outputs, [], 1.0)
except Exception as e:
print(e)
break
for inp in inputsReady:
if inp == self.__clientSocket:
try:
data = self.__clientSocket.recv(4096)
#print(data)
#data = b""
#while not main_queue.empty():
# data += main_queue.get()
except Exception as e:
print(e)
if data != None:
if len(data) > 0:
targetHostData += data
#else:
# terminate = True
elif inp == targetHostSocket:
try:
data = b""
while not main_queue.empty():
data += main_queue.get()
except Exception as e:
print(e)
if data != None:
if len(data) > 0:
clientData += data
for out in outputsReady:
if out == self.__clientSocket and len(clientData) > 0:
#pck = Ether(clientData)
#pck.show()
bytesWritten = self.__clientSocket.send(clientData)
if bytesWritten > 0:
clientData = clientData[bytesWritten:]
elif out == targetHostSocket and len(targetHostData) > 0:
#pck = Ether(targetHostData)
#pck.show()
bytesWritten = targetHostSocket.send(targetHostData)
if bytesWritten > 0:
targetHostData = targetHostData[bytesWritten:]
self.__clientSocket.close()
targetHostSocket.close()
print ("ClientThread terminating")
def handle_sniff(pck):
if IP in pck:
if pck[IP].src == "192.168.1.48":
if Raw in pck:
payload = pck[Raw].load
if b'\x12\x01\x00\x01\x00\x00\x00\x08$\x07\x04\x00\x88#\x01\x02\x00\x01' in payload:
payload = payload.replace(b'\x00\x08$\x07\x04\x00\x88#\x01\x02\x00', b'\x00\x08$\x07\x04\x00\x88\x15\x01\x02\x00')
print(payload)
main_queue.put(payload)
if __name__ == '__main__':
localHost = "localhost"
localPort = 12345
targetHost = "192.168.1.12"
targetPort = 7575
serverSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serverSocket.bind((localHost, localPort))
serverSocket.listen(5)
print("Waiting for client...")
while True:
try:
clientSocket, address = serverSocket.accept()
except KeyboardInterrupt:
print("\nTerminating...")
terminateAll = True
break
print("starting client")
ClientThread(clientSocket, targetHost, targetPort).start()
sniff(iface="Ethernet", prn=lambda pck: handle_sniff(pck))
serverSocket.close()
Once the script is running, configure the Virtual Here client to listen for USB servers at localhost:12345. The handle_sniff function is where the USB device descriptor information is being changed. Once connected you should be able to double click on the USB device in the dropdown tree. You will see the USB data begin to be printed in the your python console.
In the above example I changed the device bcdDevice bytes of the USB Descriptor.
Another helpful script I used to identify the packet that contained the information I was targeting is below. I modified a script I found in this solution. It is modified to print the raw data along with the unpacked device descriptor information, which can then be searched for in the TCP raw data to identify which bytes to replace.
#!/usr/bin/env python
from __future__ import print_function
import argparse
import string
import struct
import sys
import win32api
import win32file
import pywintypes
BUFF=b""
def CTL_CODE(DeviceType, Function, Method, Access):
return (DeviceType << 16) | (Access << 14) | (Function << 2) | Method
def USB_CTL(id):
# CTL_CODE(FILE_DEVICE_USB, (id), METHOD_BUFFERED, FILE_ANY_ACCESS)
return CTL_CODE(0x22, id, 0, 0)
IOCTL_USB_GET_ROOT_HUB_NAME = USB_CTL(258) # HCD_GET_ROOT_HUB_NAME
IOCTL_USB_GET_NODE_INFORMATION = USB_CTL(258) # USB_GET_NODE_INFORMATION
IOCTL_USB_GET_NODE_CONNECTION_INFORMATION = USB_CTL(259) # USB_GET_NODE_CONNECTION_INFORMATION
IOCTL_USB_GET_NODE_CONNECTION_DRIVERKEY_NAME = USB_CTL(264) # USB_GET_NODE_CONNECTION_DRIVERKEY_NAME
IOCTL_USB_GET_NODE_CONNECTION_NAME = USB_CTL(261) # USB_GET_NODE_CONNECTION_NAME
IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION = USB_CTL(260) # USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION
USB_CONFIGURATION_DESCRIPTOR_TYPE = 2
USB_STRING_DESCRIPTOR_TYPE = 3
USB_INTERFACE_DESCRIPTOR_TYPE = 4
MAXIMUM_USB_STRING_LENGTH = 255
def open_dev(name):
try:
handle = win32file.CreateFile(name,
win32file.GENERIC_WRITE,
win32file.FILE_SHARE_WRITE,
None,
win32file.OPEN_EXISTING,
0,
None)
except pywintypes.error as e:
return None
return handle
def get_root_hub_name(handle):
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_ROOT_HUB_NAME,
None,
6,
None)
act_len, _ = struct.unpack('LH', buf)
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_ROOT_HUB_NAME,
None,
act_len,
None)
return buf[4:].decode('utf-16le')
def get_driverkey_name(handle, index):
key_name = bytes(chr(index) + '\0'*9, 'utf-8')
try:
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_NODE_CONNECTION_DRIVERKEY_NAME,
key_name,
10,
None)
except pywintypes.error as e:
print(e.strerror, index)
sys.exit(1)
_, act_len, _ = struct.unpack('LLH', buf)
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_NODE_CONNECTION_DRIVERKEY_NAME,
key_name,
act_len,
None)
return buf[8:].decode('utf-16le')
def get_ext_hub_name(handle, index):
hub_name = chr(index) + '\0'*9
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_NODE_CONNECTION_NAME,
hub_name,
10,
None)
_, act_len, _ = struct.unpack('LLH', buf)
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_NODE_CONNECTION_NAME,
hub_name,
act_len,
None)
return buf[8:].decode('utf-16le')
def get_str_desc(handle, conn_idx, str_idx):
req = struct.pack('LBBHHH',
conn_idx,
0,
0,
(USB_STRING_DESCRIPTOR_TYPE<<8) | str_idx,
win32api.GetSystemDefaultLangID(),
MAXIMUM_USB_STRING_LENGTH)
try:
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION,
req,
12+MAXIMUM_USB_STRING_LENGTH,
None)
except pywintypes.error as e:
return 'ERROR: no String Descriptor for index {}'.format(str_idx)
if len(buf) > 16:
return buf[14:].decode('utf-16le')
return ''
def exam_hub(name, verbose, level):
handle = open_dev(r'\\.\{}'.format(name))
if not handle:
print('Failed to open device {}'.format(name))
return
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_NODE_INFORMATION,
None,
76,
None)
print_hub_ports(handle, ord(buf[6]), verbose, level)
handle.close()
def print_str_or_hex(to_be_print):
if all(c in string.printable for c in to_be_print):
print('"{}"'.format(to_be_print))
return
print('Hex: ', end='')
for x in to_be_print:
print('{:02x} '.format(ord(x)), end='')
print('')
def print_hub_ports(handle, num_ports, verbose, level):
print(handle, num_ports, verbose, level)
for idx in range(1, num_ports+1):
info = bytes(chr(idx) + '\0'*34, 'utf-8')
try:
buf = win32file.DeviceIoControl(handle,
IOCTL_USB_GET_NODE_CONNECTION_INFORMATION,
info,
34 + 11*30,
None)
except pywintypes.error as e:
print(e)
print(e.winerror, e.funcname, e.strerror)
return
print(buf)
_, vid, pid, vers, manu, prod, seri, _, ishub, _, stat = struct.unpack('=12sHHHBBB3s?6sL', buf[:35])
if ishub:
if verbose:
print('{} [Port{}] {}'.format(' '*level, idx, 'USB Hub'))
exam_hub(get_ext_hub_name(handle, idx), verbose, level)
elif stat == 0 and verbose:
print('{} [Port{}] {}'.format(' '*level, idx, 'NoDeviceConnected'))
elif stat == 1:
if verbose or (manu != 0 or prod != 0 or seri != 0):
print('{} [Port{}] {}'.format(' '*level, idx, get_driverkey_name(handle, idx)))
print('{} Vendor ID: 0x{:04X}'.format(' '*level, vid))
print('{} Product ID: 0x{:04X}'.format(' '*level, pid))
print('{} Device BCD: 0x{:04X}'.format(' '*level, vers))
print(vers)
if manu != 0:
print('{} Manufacturer (0x{:x}) -> '.format(' '*level, manu), end='')
print_str_or_hex(get_str_desc(handle, idx, manu))
if prod != 0:
print('{} Product (0x{:x}) -> '.format(' '*level, prod), end='')
print_str_or_hex(get_str_desc(handle, idx, prod))
if seri != 0:
print('{} Serial No (0x{:x}) -> '.format(' '*level, seri), end='')
print_str_or_hex(get_str_desc(handle, idx, seri))
def main():
parser = argparse.ArgumentParser()
parser.add_argument('-v', '--verbose', action='store_true',
help="Increase output verbosity.")
args = parser.parse_args()
for i in range(10):
name = r"\\.\HCD{}".format(i)
handle = open_dev(name)
if not handle:
continue
root = get_root_hub_name(handle)
print('{}RootHub: {}'.format('\n' if i != 0 else '', root))
dev_name = r'\\.\{}'.format(root)
dev_handle = open_dev(dev_name)
if not dev_handle:
print('Failed to open device {}'.format(dev_name))
continue
buf = win32file.DeviceIoControl(dev_handle,
IOCTL_USB_GET_NODE_INFORMATION,
None,
76,
None)
global BUFF
BUFF=buf
print_hub_ports(dev_handle, buf[6], args.verbose, 0)
dev_handle.close()
handle.close()
if __name__ == '__main__':
main()
P.S. This is also really helpful for filtering and modifying any of the USB data being transferred not just the device descriptor.
I used python to make a prototype, to increase the volume of audio signal in real time. It worked by using new_data = audioop.mul(data, 4, 4) where 'data' is chunks from Pyaudio in streaming.
Now, I have to apply similar in ObjectiveC, and even after searching I am unable to find it. How can it be done in Objective C? Do we have such control over data flow in Objective C and If we can't, Is there anyway that a recorded sample's volume can be increased?
import pyaudio
import wave
import audioop
import sys
FORMAT = pyaudio.paInt16
CHANNELS = 1
RATE = 44100
CHUNK = 1024
RECORD_SECONDS = 7
WAVE_OUTPUT_FILENAME1 = sys.argv[1]
WAVE_OUTPUT_FILENAME2 = sys.argv[2]
device_index = 2
print("----------------------record device list---------------------")
audio = pyaudio.PyAudio()
print(audio)
info = audio.get_host_api_info_by_index(0)
numdevices = info.get('deviceCount')
for i in range(0, numdevices):
if (audio.get_device_info_by_host_api_device_index(0, i).get('maxInputChannels')) > 0:
print ("Input Device id ", i, " - ", audio.get_device_info_by_host_api_device_index(0, i).get('name'))
print("-------------------------------------------------------------")
index = int((input()))
print(type(index))
print("recording via index "+str(index))
stream = audio.open(format=FORMAT, channels=CHANNELS,
rate=RATE, input=True,input_device_index = index,
frames_per_buffer=CHUNK)
print ("recording started")
Recordframes = []
Recordframes2= []
print(int(RATE / CHUNK * RECORD_SECONDS))
for i in range(0, int(RATE / CHUNK * RECORD_SECONDS)):
data = stream.read(CHUNK)
new_data = audioop.mul(data, 4, 4)
print("hshsh")
Recordframes.append(data)
Recordframes2.append(new_data)
# data = stream.read(CHUNK)
# print("hshsh")
# Recordframes.append(data)
# print ("recording stopped")
stream.stop_stream()
stream.close()
audio.terminate()
waveFile = wave.open(WAVE_OUTPUT_FILENAME1, 'wb')
waveFile.setnchannels(CHANNELS)
waveFile.setsampwidth(audio.get_sample_size(FORMAT))
waveFile.setframerate(RATE)
waveFile.writeframes(b''.join(Recordframes))
waveFile2 = wave.open(WAVE_OUTPUT_FILENAME2, 'wb')
waveFile2.setnchannels(CHANNELS)
waveFile2.setsampwidth(audio.get_sample_size(FORMAT))
waveFile2.setframerate(RATE)
waveFile2.writeframes(b''.join(Recordframes2))
waveFile.close()
waveFile2.close()
You can use AVAudioEngine (link) to tap into the raw audio data. Alternatively, still using AVAudioEngine, you could add an AVAudioUnitEQ (link) node to your audio graph and use that boost the gain.
Using either method, you can then write out to a file using AVAudioFile (link).
I'm working on a project where I'm trying to convert old 16bit binary data files into 32bit data files for later use.
Straight conversion is no issue, but then i noticed i needed to remove header data from the data-file's.
The data consists of 8206 bytes long frames, each frame consists of 14 byte long header and 4096 bytes long data -block, depending on file, there are either 70313 or 70312 frames in each file.
i couldn't find a neat way to find all the header and remove them and save only the data-block to a new file.
so heres what I did:
results_array = np.empty([0,1], np.uint16)
for filename in file_list:
num_files += 1
# read data from file as 16bit's and save it as 32bit
data16 = np.fromfile(data_dir + "/" + filename, dtype=np.uint16)
filesize = np.prod(data16.shape)
if filesize == 288494239:
total_frames = 70313
#total_frames = 3000
else:
total_frames = 70312
#total_frames = 3000
frame_count = 0
chunksize = 4103
with open(data_dir + "/" + filename, 'rb') as file:
while frame_count < total_frames:
frame_count += 1
read_data = file.read(chunksize)
if not read_data:
break
data = read_data[7:4103]
results_array = np.append(results_array,data)
converted = np.frombuffer(results_array, np.uint16)
print(str(frame_count) + "/" + str(total_frames))
converted = np.frombuffer(results_array, np.uint16)
data32 = converted.astype(dtype=np.uint32) * 256
It works (i think it does atleast), but it is very very slow.
So question is, is there a way to do the above much faster, maybe some build-in function in numpy or something else perhaps?
Thanks in advance
Finally managed to crack this one, and it is 100x faster than initial approach :)
data = np.fromfile(read_dir + "/" + file, dtype=np.int16)
frames = len(data) // 4103 # framelenght
# Reshape into array such that each row is a frame
data = np.reshape(data[:frames * 4103], (frames, 4103))
# Remove headers and convert to int32
data = data[:, 7:].astype(np.int32) * 256
I was hoping someone may be able to see where I am failing here. So I have scraped some data from buzzfeed and now I am trying to format a text file with which I can then send into data_convert_examples text_to_data formatter.
I thought I had the answer a couple times, but I am still running up against a brick wall when I process this as binary and then try to train against the data.
What I did was run the binary_to_text on the toy dataset and then opened the file in notepad++ under windows, showing all characters, and matched what I believed to be the format.
I appologize for the long function below, but I really am unsure as to where the issue might be and figured this was the best way to provide enough info. Anyone have any ideas or recommendations?
def processPath(self, toPath):
try:
fout = open(os.path.join(toPath, '{}-{}'.format(self.baseName, self.fileNdx)), 'a+')
for path, dirs, files in os.walk(self.fromPath):
for fn in files:
fullpath = os.path.join(path, fn)
if os.path.isfile(fullpath):
#with open(fullpath, "rb") as f:
with codecs.open(fullpath, "rb", 'ascii', "ignore") as f:
try:
finalRes = ""
content = f.readlines()
self.populateVocab(content)
sentences = sent_tokenize((content[1]).encode('ascii', "ignore").strip('\n'))
for sent in sentences:
textSumFmt = self.textsumFmt
finalRes = textSumFmt["artPref"] + textSumFmt["sentPref"] + sent.replace("=", "equals") + textSumFmt["sentPost"] + textSumFmt["postVal"]
finalRes += (('\t' + textSumFmt["absPref"] + textSumFmt["sentPref"] + (content[0]).strip('\n').replace("=", "equals") + textSumFmt["sentPost"] + textSumFmt["postVal"]) + '\t' +'publisher=BUZZ' + os.linesep)
if self.lineNdx != 0 and self.lineNdx % self.lines == 0:
fout.close()
self.fileNdx+=1
fout = open(os.path.join(toPath, '{}-{}'.format(self.baseName, self.fileNdx)), 'a+')
fout.write( ("{}").format( finalRes.encode('utf-8', "ignore") ) )
self.lineNdx+=1
except RuntimeError as e:
print "Runtime Error: {0} : {1}".format(e.errno, e.strerror)
finally:
fout.close()
After further analysis, it seems that the source of the problem is more with the source data and the way it is constructed rather than data_convert_example.py itself. I'm closing this as the heading is not in-line with the source of the issue.
I found the source of my problem was that I had a space between "Article" and the equals sign. After removing that I was able to successfully train.
The following is a hex-ascii dump of the first 300 bytes of an avi xvid file:
|52|49|46|46|8c|79|95|00|41|56|49|20|4c|49|53|54|94|6a|00|00 RIFF.y..AVI LIST.j..
|68|64|72|6c|61|76|69|68|38|00|00|00|40|9c|00|00|00|ec|36|00 hdrlavih8...#.....6.
|00|00|00|00|10|00|00|00|81|01|00|00|00|00|00|00|01|00|00|00 ....................
|df|9e|01|00|d0|02|00|00|40|02|00|00|00|00|00|00|00|00|00|00 ........#...........
|00|00|00|00|00|00|00|00|4c|49|53|54|3c|69|00|00|73|74|72|6c ........LIST<i..strl
|73|74|72|68|38|00|00|00|76|69|64|73|78|76|69|64|00|00|00|00 strh8...vidsxvid....
|00|00|00|00|00|00|00|00|e8|03|00|00|a8|61|00|00|00|00|00|00 .............a......
|81|01|00|00|df|9e|01|00|10|27|00|00|00|00|00|00|00|00|00|00 .........'..........
|d0|02|40|02|73|74|72|66|28|00|00|00|28|00|00|00|d0|02|00|00 ..#.strf(...(.......
|40|02|00|00|01|00|18|00|58|56|49|44|00|f8|25|00|00|00|00|00 #.......XVID..%.....
|00|00|00|00|00|00|00|00|00|00|00|00|73|74|72|64|c0|28|00|00 ............strd.(..
|00|00|00|00|bc|02|00|00|90|b2|08|00|2e|5c|76|69|64|65|6f|2e .............\video.
|70|61|73|73|00|00|2e|00|70|00|61|00|73|00|73|00|00|00|00|00 pass....p.a.s.s.....
|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00 ....................
|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00|00 ....................
In this particular case I know that the video has a frame rate of 25 frames per second. How can I use this dump to obtain the frame rate? Note, it is straightforward to obtain the frame rate for an avi msvc video file since the data structure is well documented. However, I have yet to find any document that defines the data structure for an avi xvid file.
The following is an improved version (IMHO) of my previous answer. This code finds 5 key features of AVI files.
"""
Purpose: To extract 5 important features from AVI files: time between frames,
frames per second, number of frames, width and height of each frame.
Author: V. Stokes (vs#it.uu.se)
Version: 2014.01.01.1
Note:
1. DT (time between samples) in microseconds, bytes: 32,33,34,35
of all AVI files that I tested. Byte 0 is the first byte in the AVI file.
2. SR (sample rate) is equivalent to fps (frames per second) and can be
calculated from the inverse of DT.
3. NF (number of frames), bytes: 48,49,50,51.
4. WD (width of each frame) in pixels, bytes: 64,65,66,67
5. HT (height of each frame) in pixels, bytes: 68,69,70,71
6. This python script works on all the AVI files that I have tested (so far),
which suggests there is some consistency in the different AVI formats.
"""
import os
# laptop desktop
dirpaths = [r'D:/Videos/', r'C:/Videos/']
for path in dirpaths:
if os.path.exists(path):
defDir = path
## All the following videos were "test AVI video downloads" from the Web
#video = 'julius.avi' #CRAM ( 56 frames,320x240,15fps, 66667 microseconds between frames)
#video = 'flyby-xvid.avi' #DIVX (495 frames,320x240,30fps, 33333 microseconds between frames)
#video = 'flyby-xvid-realtime.avi' #DIVX (495 frames,320x240,30fps, 33333 microseconds between frames)
#video = 'flyby-xvid-q5.avi' #DIVX
#video = 'flyby-xvid-mpeg.avi' #DIVX
#video = 'flyby-xvid-mpeg-q2.avi' #DIVX
#video = 'flyby-xvid-default.avi' #DIVX
#video = 'flyby-xvid-2p.avi' #DIVX
#video = 'flyby-divx.avi' #DX50
#video = 'ubAVIxvid10.avi' #XVID (849 frames,640x480,10fps,100000 microseconds between frames)
#video = 'toy_plane_liftoff.mp4' # This is not an AVI and doesn't work
video = 'toy_plane_liftoff.avi' #MJPG (100 frames,640x480,25fps, 40000 microsseconds between frames)
inFile = defDir + video
print 'Input file: %s' %inFile
data = [0,0,0,0]
with open(inFile,'r') as f:
f.seek(32,0) # start reading offset byte 32
data[0] = f.read(4) # get 4 bytes (32,33,34,35) -- DT
f.seek(48,0)
data[1] = f.read(4) # get 4 bytes (48,49,50,51) -- NF
f.seek(64,0)
data[2] = f.read(4) # get 4 bytes (64,65,66,67) -- Width
data[3] = f.read(4) # get 4 bytes (68,69,70,71) -- Height
f.close()
def bufferToHex(num):
for k in range(num):
accumulator = ''
buffer = data[k]
for item in range(4):
accumulator += '%s' % buffer[item]
data[k] = accumulator
# Get 4 hex strings (4 bytes in each string)
bufferToHex(4)
for k in range(4): # loop on DT,NF,WD,HT
prev_kvs = ''
for hexval in data[k]: # loop on each group of 4 bytes
strr = hexval.encode('hex') # hexidecimal string of length 2
kvs = strr + prev_kvs
prev_kvs = kvs
intVal = int(kvs,16)
if k == 0:
# DT
print 'DT = %6d (microseconds)' %intVal
print 'SR = %6d (frames per second)' %round(10.0**6/intVal)
elif k == 1:
# NF
print 'NF = %6d (number of frames)' %intVal
elif k == 2:
# Width
print 'Width = %6d (width in pixels)' %intVal
else:
# Height
print 'Height = %6d (height in pixels)' %intVal
The following Python script (Python 2.7, Windows Vista-32 bit) can be used to extract the time between frames from AVI files and in turn the frame rate.
"""
Purpose: To extract the time between frames from AVI files
Author: V. Stokes (vs#it.uu.se)
Version: 2013.12.31.1
Note:
1. DT (time between samples) in microseconds is stored in bytes: 32,33,34,35
of all AVI files that I tested. Byte 0 is the first byte in the AVI file.
2. SR (sample rate) is equivalent to fps (frames per second) and can be
calculated from the inverse of DT.
3. DT is stored as 4 bytes (long C integer) which are in reverse order.
4. This python script works on all the AVI files that I have tested (so far),
which suggests there is some consistency in the different AVI formats.
5. All of the AVI files used for testing can be obtained from me via
an email request.
"""
import os
# laptop desktop
dirpaths = [r'D:/Videos/', r'C:/Videos/']
for path in dirpaths:
if os.path.exists(path):
defDir = path
#
## All of the following files were downloaded from different web "test" AVI file sites
## Bytes: 32,33,34,35 = 35,82,00,00
#video = 'flyby-xvid.avi' #DIVX (495 frames,320x240,30fps, 33333 microseconds between frames)
#video = 'flyby-xvid-realtime.avi' #DIVX (495 frames,320x240,30fps, 33333 microseconds between frames)
#video = 'flyby-xvid-q5.avi' #DIVX
#video = 'flyby-xvid-mpeg.avi' #DIVX
#video = 'flyby-xvid-mpeg-q2.avi' #DIVX
#video = 'flyby-xvid-default.avi' #DIVX
#video = 'flyby-xvid-2p.avi' #DIVX
## Bytes: 32,33,34,35 = 35,82,00,00
#video = 'flyby-divx.avi' #DX50
## Bytes: 32,33,34,35 = a0,86,01,00
#video = 'ubAVIxvid10.avi' #XVID (849 frames,640x480,10fps,100000 microseconds between frames)
#video = 'toy_plane_liftoff.mp4' # This is not an AVI and doesn't work!
#video = 'toy_plane_liftoff.avi' #MJPG (100 frames,640x480,25fps, 40000 microsseconds between frames)
## Bytes: 32,33,34,35 = 6b,04,01,00
video = 'julius.avi' #CRAM ( 56 frames,320x240,15fps, 66667 microseconds between frames)
inFile = defDir+video
print 'Input file: %s' %inFile
with open(inFile,'r') as f:
# Get time between frames (in hex format)
f.seek(32,0) # start reading at byte 32
data = f.read(4) # get 4 bytes (32,33,34,35)
f.close()
def bufferToHex(buffer, start, count):
accumulator = ''
for item in range(count):
accumulator += '%s' % buffer[start + item]
return accumulator
hexc = bufferToHex(data, 0, 4)
timeBetweenFrames = 0
k = -2
for hexval in hexc:
k += 2 # two hex characters
kvs = hexval.encode('hex') # hexidecimal string of length 2
kv = int(kvs,16) # convert to integer base-16 (hexidecimal)
kp = 16**k
timeBetweenFrames += kv*kp
print 'DT = %6d (microseconds)' %timeBetweenFrames
print 'SR = %6d (frames per second)' %round(10.0**6/timeBetweenFrames)