Updating Video Metadata¶

In addition of using metadata property object in FFdecoder API for probing metadata information (only as JSON string) for each multimedia stream available in the given video source, you can also easily update the video metadata on-the-fly by assigning desired data as python dictionary to the same overloaded metadata property object. This feature can be used either for adding new custom properties to metadata, or to override source metadata properties used by FFdecoder API to formulate its default Decoder Pipeline for real-time video-frames generation.

We'll discuss video metadata extraction using both these APIs briefly in the following recipes:

Added new properties to metadata in FFdecoder API¶

In FFdecoder API, you can easily define any number of new properties for its metadata (formatted as python dictionary) with desired data of any datatype(s)¹ , without affecting its default Video frames Decoder pipeline.

In this example we will probe all metadata information available within foo.mp4 video file on Windows machine, thereby add new propertys (formatted as python dictionary) with desired data of different datatype(s) through overloaded metadata property object, and then finally print it as JSON string using the same metadata property object in FFdecoder API.

# import the necessary packages
from deffcode import FFdecoder
import json

# initialize the decoder using suitable source
decoder = FFdecoder("foo.mp4", verbose=True)

# format your data as dictionary (with data of any [printable] datatype)
data = dict(
    mystring="abcd",  # string data
    myint=1234,  # integers data
    mylist=[1, "Rohan", ["inner_list"]],  # list data
    mytuple=(1, "John", ("inner_tuple")),  # tuple data
    mydict={"anotherstring": "hello"},  # dictionary data
    myjson=json.loads('{"name": "John", "age": 30, "city": "New York"}'),  # json data
)

# assign your dictionary data
decoder.metadata = data

# finally formulate the decoder
decoder.formulate()

# print metadata as `json.dump`
print(decoder.metadata)

# terminate the decoder
decoder.terminate()

{
  "ffmpeg_binary_path": "C:\\Users\\foo\\AppData\\Local\\Temp\\ffmpeg-static-win64-gpl/bin/ffmpeg.exe",
  "source": "D:\\foo.mp4",
  "source_extension": ".mp4",
  "source_video_resolution": [
    1920,
    1080
  ],
  "source_video_framerate": 29.97,
  "source_video_pixfmt": "yuv420p",
  "source_video_decoder": "h264",
  "source_duration_sec": 21.03,
  "approx_video_nframes": 630,
  "source_video_bitrate": "4937k",
  "source_audio_bitrate": "256k",
  "source_audio_samplerate": "48000 Hz",
  "source_has_video": true,
  "source_has_audio": true,
  "source_has_image_sequence": false,
  "ffdecoder_operational_mode": "Video-Only",
  "output_frames_pixfmt": "rgb24",
  "mystring": "abcd",
  "myint": 1234,
  "mylist": [
    1,
    "Rohan",
    [
      "inner_list"
    ]
  ],
  "mytuple": [
    1,
    "John",
    "inner_tuple"
  ],
  "mydict": {
    "anotherstring": "hello"
  },
  "myjson": {
    "name": "John",
    "age": 30,
    "city": "New York"
  }
}

Overriding source video metadata in FFdecoder API¶

In FFdecoder API, you can also use its metadata to manually override the source properties (as frame-size, frame pixel-format, video-framerate, video-decoder etc.) that directly affects its default Video frames Decoder pipeline that decodes real-time video-frames.

In this example we will probe all metadata information available within foo.mp4 video file, and override frame size (originally 1920x1080) and pixel-format (originally rgb24) to our desired values through overloaded metadata property object in FFdecoder API, and thereby preview them using OpenCV Library's cv2.imshow() method.

# import the necessary packages
from deffcode import FFdecoder
import cv2

# initialize and formulate the decoder using suitable source
decoder = FFdecoder("foo.mp4", verbose=True)

# override source metadata values
# !!! [WARNING] Make sure each value datatype matches the table !!!
decoder.metadata = {
    "output_frames_pixfmt": "gray",  # gray frame-pixfmt
    "source_video_resolution": [1280, 720],  # 1280x720 frame-size
}

# finally formulate the decoder
decoder.formulate()

# [NOTE] uncomment following line to debug values
# print(decoder.metadata)

# let's grab the 1280x720 sized gray frames from decoder
for frame in decoder.generateFrame():

    # check if frame is None
    if frame is None:
        break

    # {do something with gray frame here}

    # Show gray frames in output window
    cv2.imshow("Output gray", frame)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# terminate the decoder
decoder.terminate()