Downloading the first frame of a twitch.tv stream

Question

Using this api I've managed to download stream data, but I can't figure out how to parse it. I've looked at the RMTP format, but it doesn't seem to match.

from livestreamer import Livestreamer

livestreamer = Livestreamer()

# set to a stream that is actually online
plugin = livestreamer.resolve_url("http://twitch.tv/froggen")
streams = plugin.get_streams()
stream = streams['mobile_High']
fd = stream.open()
data = fd.read()

I've uploaded an example of the data here.

Ideally I wouldn't have to parse it as video, I only need the first keyframe as an image. Any help would be greatly appreciated!

Update: Ok, I got OpenCV working, it works for grabbing the first frame of a random video file I had. However, it produced a nonsense image when I used the same code on file with stream data.

Answer 1

Alright, I figured it out. Made sure to write as binary data, and OpenCV is able to decode the first video frame. The resulting image had R and B channels switched, but that was easily corrected. Downloading about 300 kB seems to be enough to be sure that the full image is there.

import time, Image

import cv2
from livestreamer import Livestreamer

# change to a stream that is actually online
livestreamer = Livestreamer()
plugin = livestreamer.resolve_url("http://twitch.tv/flosd")
streams = plugin.get_streams()
stream = streams['mobile_High']

# download enough data to make sure the first frame is there
fd = stream.open()
data = ''
while len(data) < 3e5:
    data += fd.read()
    time.sleep(0.1)
fd.close()

fname = 'stream.bin'
open(fname, 'wb').write(data)
capture = cv2.VideoCapture(fname)
imgdata = capture.read()[1]
imgdata = imgdata[...,::-1] # BGR -> RGB
img = Image.fromarray(imgdata)
img.save('frame.png')
# img.show()