Lossless Video and Audio Merging Guide

Guide to Lossless Video and Audio Merging

How Lossless Merging Works:

To ensure lossless merging of video and audio streams, we use specific flags in our script:

  • Copying Streams: The -c:v copy and -c:a copy flags in the postprocessor_args ensure that both the video and audio streams are copied directly from the source without any modification, preserving their original quality.
  • No Re-Encoding: Since the streams are not re-encoded, the output file retains the original quality of the downloaded video and audio streams.

Ensuring Lossless Quality:

When using yt-dlp, the merging process is designed to maintain the highest possible quality:

  • Video Quality: The selected video stream (e.g., hlsv6-1102) is copied as-is, using the HEVC codec (hvc1.1.6.L93.90), ensuring efficient compression with good quality.
  • Audio Quality: The audio stream (e.g., hlsv6-default-audio-group-English-1) is copied as-is, preserving the original AAC audio without any compression or re-encoding.

Confirming the Quality:

You can confirm that the merging process is indeed lossless by checking the properties of the final output file:

  • Video Codec and Bitrate: Should match the source stream.
  • Audio Codec and Bitrate: Should match the source stream.

Use a media info tool (like MediaInfo) to inspect the properties of the final merged file and compare them to the original streams.

Considerations for Audio Quality:

The audio stream in this case is AAC (Advanced Audio Codec), a common format for streaming services. While AAC is a lossy format by nature, the process of copying it as-is ensures that the original quality provided by the stream is preserved.

If AAC is the highest quality format available from the source, this process will ensure that you get the best possible quality.

Conclusion:

The merging process with yt-dlp using the provided script is indeed lossless for both video and audio. The final output file should retain the highest possible quality for both streams as provided by the source, without any further compression or quality loss during the merging process.

Steps to Run the Script:

  1. Install yt-dlp: Ensure you have yt-dlp installed in your environment. You can install it using pip if you haven't already:
    2. pip install yt-dlp
  2. Run the Script: Execute the script in your Python environment. It will download the video with the best available video and audio formats and merge them into an MP4 file.
  3. Check the Download: The video file will be saved in the C:/Users/liber8/Downloads/ directory with the title Spread.mp4.
Note: The selected video format uses the HEVC codec (hvc1), which provides efficient compression with good quality. The audio format is specified as AAC, and it's combined with the video without re-encoding to preserve the original quality.

Available Formats Summary:

To download the best quality video with the corresponding audio, use the following format IDs:

  • Video Format ID: hlsv6-1102
  • Audio Format ID: hlsv6-default-audio-group-English-1

Download Script Using yt-dlp:

You can use the following Python script to download the video and audio, and merge them into a single MP4 file:


import yt_dlp

# The initial URL to download
initial_url = "http://link.tubi.tv/a/key_live_engWioqI5aBmxG8T9gTYCdiorCj8H2Th?channel=mobile_web&feature=mobile_web&contentType=movie&contentId=100008485&action=media-details"

# Options for yt-dlp
ydl_opts = {
    'format': 'hlsv6-1102+hlsv6-default-audio-group-English-1',  # Specify the best video and audio format IDs
    'outtmpl': 'C:/Users/liber8/Downloads/%(title)s.%(ext)s',  # Output filename template
    'merge_output_format': 'mp4',  # Merge into mp4 format
    'postprocessor_args': [
        '-c:v', 'copy',  # Copy video stream without re-encoding
        '-c:a', 'copy'   # Copy audio stream without re-encoding
    ],
    'writeinfojson': True,  # Save metadata
    'writethumbnail': True,  # Download and embed thumbnails
    'quiet': False,  # Show output
    'verbose': True,  # Verbose output for debugging
}

# Create a yt-dlp instance with the options
with yt_dlp.YoutubeDL(ydl_opts) as ydl:
    # Download the video with the best video and audio
    ydl.download([initial_url])

Download the Desired Format:

To download and merge the video into an MKV container instead of MP4, use the following modified script:


import yt_dlp

# The initial URL to download
initial_url = "http://link.tubi.tv/a/key_live_engWioqI5aBmxG8T9gTYCdiorCj8H2Th?channel=mobile_web&feature=mobile_web&contentType=movie&contentId=100008485&action=media-details"

# Options for yt-dlp
ydl_opts = {
    'format': 'hlsv6-1102+hlsv6-default-audio-group-English-1',  # Specify the best video and audio format IDs
    'outtmpl': 'C:/Users/liber8/Downloads/%(title)s.%(ext)s',  # Output filename template
    'merge_output_format': 'mkv',  # Merge into MKV format instead of MP4
    'postprocessor_args': [
        '-c:v', 'copy',  # Copy video stream without re-encoding
        '-c:a', 'copy'   # Copy audio stream without re-encoding
    ],
    'writeinfojson': True,  # Save metadata
    'writethumbnail': True,  # Download and embed thumbnails
    'quiet': False,  # Show output
    'verbose': True,  # Verbose output for debugging
}

# Create a yt-dlp instance with the options
with yt_dlp.YoutubeDL(ydl_opts) as ydl:
    # Download the video with the best video and audio
    ydl.download([initial_url])

Media Info Results:

MP4 Container:


General
Complete name                            : C:\Users\Liber8\Downloads\Spread.mp4
Format                                   : MPEG-4
File size                                : 742 MiB
Duration                                 : 1 h 33 min
Overall bit rate                         : 1 104 kb/s
Frame rate                               : 23.976 FPS
Writing application                      : Lavf61.1.100

Video
Format                                   : HEVC
Codec ID                                 : hev1
Bit rate                                 : 970 kb/s
Width                                    : 1 280 pixels
Height                                   : 608 pixels
Display aspect ratio                     : 2.105
Frame rate                               : 23.976 FPS

Audio
Format                                   : AAC LC
Codec ID                                 : mp4a-40-2
Bit rate                                 : 128 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 kHz

MKV Container:


General
Complete name                            : C:\Users\Liber8\Downloads\Spread.mkv
Format                                   : Matroska
File size                                : 740 MiB
Duration                                 : 1 h 33 min
Overall bit rate                         : 1 102 kb/s
Frame rate                               : 23.976 FPS

Video
Format                                   : HEVC
Codec ID                                 : V_MPEGH/ISO/HEVC
Width                                    : 1 280 pixels
Height                                   : 608 pixels
Display aspect ratio                     : 2.105
Frame rate                               : 23.976 FPS

Audio
Format                                   : AAC LC
Codec ID                                 : A_AAC-2
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 kHz

© 2024 Lossless Video and Audio Merging Guide

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