video_utils.audio package

Submodules

video_utils.audio.audio_delay module

Determine audio delay between files

Using the audio_delay() function, the delay between audio files can be determined. This is done using the cross-correlation between the two files and using the lag/lead at which the correlation is the largest.

There is also a function that can be used to visualize the delay between the two files, and the accuracy of this method at aligning them.

video_utils.audio.audio_delay.audio_delay(file1, file2, show_plots: bool = False, limit: int | None = None)

Compute delay between audio in different video files

Motivation behind this function was to add surround sound tracks to videos that only contined stereo downmixes, but were higher video resolution (say 720p) than the source of the surround tracks (say 480p from DVD).

Parameters:

  • file1 (str) – Path to file to align to

  • file2 (str) – Path to file to align

Keyword Arguments:

  • show_plots (bool) – If true, try to display plots of alignment

  • limit (int) – Length of audio file (in minutes) to use to align

Returns:

Delay (in seconds) as float and as formatted string

Return type:

tuple

video_utils.audio.audio_delay.fft_xcorr(samples1, samples2)

Compute scaled cross-correlation using ffts

Compute the cross-correlation between two audio files to determine time delay

Parameters:

  • samples1 (numpy.ndarray) – Samples from first audio file

  • samples2 (numpy.ndarray) – Samples from second audio file

video_utils.audio.audio_delay.plot_signals(signal1, signal2, fs, delay_mean)

Function to plot the signals to show the alignment.

video_utils.audio.dolby_downmix module

Downmixing of surround audio

video_utils.audio.dolby_downmix.dolby_downmix(infile, outdir: str | None = None, pro_logic_2: bool = True, aac: bool = False, flac: bool = False, time: str | None = None)

Downmix surround sound channels (5.1+) to Dolby Pro Logic II

A function that downmixes surround sound channels (5.1+) in a video file to Dolby Pro Logic II.

Information can be found starting in section 7.8 on page 91 of http://www.atsc.org/wp-content/uploads/2015/03/A52-201212-17.pdf and at: http://forum.doom9.org/showthread.php?s=&threadid=27936

Parameters:

infile (str) – Full path to the file that should be downmixed

Keyword Arguments:

  • pro_logic_2 (bool) – Set to downmix to Dolby Pro Logic II. This is the default. Setting to False will downmix in Dolby Pro Logic.

  • flac (bool) – Set to output as FLAC encoded file. Default is OGG.

  • aac (bool) – Set to output as AAC encoded file. Default is OGG.

  • time (str) – String in format HH:MM:SS.0 specifing the length of the downmix. Default is complete stream.

Returns:

A stereo downmix of audio tracks in infile with the same name

as input. Only first audio stream is downmixed

Return type:

None

video_utils.audio.dolby_downmix.get_downmix_filter(pro_logic_2: bool = True)

Get format string for downmix filter

Function to return an filter string for FFmpeg audio filter to downmix surround audio channels to Dolby Pro Logic or Dolby Pro Logic II

Parameters:

None –

Keyword Arguments:

pro_logic_2 – Set to use Dolby Pro Logic II downmix. This is the default

Returns:

Format string for filter

Return type:

str

video_utils.audio.replace_audio_streams module

Replace audio stream(s) in video file

Given two video files, replace the audio streams in one with the streams from another. Audio from the second file is time aligned to the first file to reduce/eliminate audio/video sync issues.

video_utils.audio.replace_audio_streams.compute_offset(in1: str, in2: str, info1: dict, info2: dict, outdir: str)

Function to get offset between files.

video_utils.audio.replace_audio_streams.extract_audio(info: dict, infile: str, outdir: str, result: list, time: timedelta | None = None)

A function to extract an audio stream from a video file

Parameters:

  • info – Information about the audio strem to extract

  • infile – Full path to the file to extract the stream from

Keyword Arguments:

  • time (timedelta) – How long the extracted stream should be.

  • lossless (bool) – Set to True to extract into a FLAC file. Only valid when stream is > 2 channels.

Returns:

Path to the extracted audio stream

Return type:

str

video_utils.audio.replace_audio_streams.file_name_info(infile: str, info: dict | None = None)

A function to get information for naming a file

Parameters:

infile (str) – Full path to the file to get information for

Keyword Arguments:

None –

Returns:

List with file information

Return type:

list

video_utils.audio.replace_audio_streams.replace_audio_streams(in1: str, in2: str, outdir: str | None = None, replace: bool = False)

Replace audio streams in one file with those from another.

This function will replace all audio streams in in1 with those in in2. If all audio streams in in2 are surround (i.e., > 2 channels), one downmixed stream will also be placed in in1.

Module contents