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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_FOURCC
import sys
from subprocess import Popen, PIPE
import re
class ffmpeg_reader:
""" 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):
""" 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']):
self.set(CAP_PROP_FRAME_WIDTH, probe['streams'][0]['width'])
if self.get(CAP_PROP_FRAME_HEIGHT) == 0 or self.get(CAP_PROP_FRAME_HEIGHT) > int(probe['streams'][0]['height']):
self.set(CAP_PROP_FRAME_HEIGHT, probe['streams'][0]['height'])
args = ["ffmpeg", "-f", self.device_format, "-list_formats", "all", "-i", self.device_name]
process = Popen(args, stdout=PIPE, stderr=PIPE)
out, err = process.communicate()
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):
""" Record a video, saving it to self.video array for processing later """