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using ffmpeg to grab resolution to save 700ms on startup

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This commit is contained in:
Tim Welch 2018-12-11 19:00:55 -05:00
parent 693eef964a
commit 546015d973
1 changed files with 28 additions and 5 deletions
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33
src/ffmpeg_reader.py
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@ -4,6 +4,8 @@ from cv2 import CAP_PROP_FRAME_WIDTH
from cv2 import CAP_PROP_FRAME_HEIGHT from cv2 import CAP_PROP_FRAME_HEIGHT
from cv2 import CAP_PROP_FOURCC from cv2 import CAP_PROP_FOURCC
import sys import sys
from subprocess import Popen, PIPE
import re
class ffmpeg_reader: class ffmpeg_reader:
""" This class was created to look as similar to the openCV features used in Howdy as possible for overall code cleanliness. """ """ This class was created to look as similar to the openCV features used in Howdy as possible for overall code cleanliness. """
@ -41,12 +43,33 @@ class ffmpeg_reader:
def probe(self): def probe(self):
""" Probe the video device to get height and width info """ """ Probe the video device to get height and width info """
probe = ffmpeg.probe(self.device_name)
if self.get(CAP_PROP_FRAME_WIDTH) == 0 or self.get(CAP_PROP_FRAME_WIDTH) > int(probe['streams'][0]['width']): args = ["ffmpeg", "-f", self.device_format, "-list_formats", "all", "-i", self.device_name]
self.set(CAP_PROP_FRAME_WIDTH, probe['streams'][0]['width']) process = Popen(args, stdout=PIPE, stderr=PIPE)
if self.get(CAP_PROP_FRAME_HEIGHT) == 0 or self.get(CAP_PROP_FRAME_HEIGHT) > int(probe['streams'][0]['height']): out, err = process.communicate()
self.set(CAP_PROP_FRAME_HEIGHT, probe['streams'][0]['height'])
if not err:
print("Error opening subprocess for ffmpeg.\n\n%s" % err)
sys.exit(1)
regex = re.compile('\s\d{3,4}x\d{3,4}')
probe = regex.findall(str(err.decode("utf-8")))
if len(probe) < 1:
# Could not determine the resolution from v4l2-ctl call. Reverting to ffmpeg.probe()
probe = ffmpeg.probe(self.device_name)
height = probe['streams'][0]['height']
width = probe['streams'][0]['width']
else:
(height, width) = [x.strip() for x in probe[0].split('x')]
if height.isdigit() and self.get(CAP_PROP_FRAME_HEIGHT) == 0:
self.set(CAP_PROP_FRAME_HEIGHT, int(height))
if width.isdigit() and self.get(CAP_PROP_FRAME_WIDTH) == 0:
self.set(CAP_PROP_FRAME_WIDTH, int(width))
def record(self, numframes): def record(self, numframes):
""" Record a video, saving it to self.video array for processing later """ """ Record a video, saving it to self.video array for processing later """