Capture OBS YouTube Live HLS Output for Debugging

Edit the hosts File to Capture the Stream

YouTube Live HLS uses a.upload.youtube.com and b.upload.youtube.com as its default addresses. When OBS sends data to one of these domains, the operating system first finds its IP address and then connects OBS to that server.

Most operating systems check the local hosts file before requesting an address from DNS. If the YouTube domain in this file points to the IP address of the PushCap server, the data that OBS sends to YouTube goes to PushCap instead.

The hosts file is a text file without an extension. Windows and Linux use the same filename but store it in different locations.

Windows

C:\Windows\System32\drivers\etc\hosts

Linux

/etc/hosts

Open the file in a text editor such as Notepad or nano. Set the YouTube upload domain to the IP address of the host running PushCap. The following example shows a Windows hosts file.

# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
#      102.54.94.97     rhino.acme.com          # source server
#       38.25.63.10     x.acme.com              # x client host
127.0.0.1	a.upload.youtube.com
# 127.0.0.1	b.upload.youtube.com
# localhost name resolution is handled within DNS itself.
#	127.0.0.1       localhost
#	::1             localhost

In this example, only the primary upload address, a.upload.youtube.com, points to the PC running PushCap. The loopback address 127.0.0.1 points to the same PC. This means that OBS and PushCap run on the same host.

The backup address starts with #, which marks the line as a comment. It is therefore not redirected. The Linux hosts file can be edited in the same way.

Capture the OBS HLS PUSH Output

After editing the hosts file, start YouTube HLS streaming in OBS. The HLS data sent to the YouTube ingest domain is then delivered to the PushCap server.

1. Select the HLS PUSH service

   Open the OBS settings, select Stream, and choose YouTube-HLS from the service list.

   

2. Set a stream key

   Select Use Stream Key, then enter any test key in the Stream Key field. The key does not need to match the normal YouTube key length. The value shown in the example was created only for this test.

   

3. Start streaming

   Select Start Streaming. After the connection succeeds, OBS uploads playlists and media segments to PushCap. The console shows each received filename and file size.

   

Check the Captured HLS Data

Stop streaming in OBS, then open the directory that contains PushCap.py. A subdirectory named uploads has been created. Inside it is another directory named after the test stream key. This directory contains the HLS data captured from OBS.

Files with the .ts extension contain the video data uploaded by OBS. Each time OBS uploads the .m3u8 playlist, PushCap also saves a numbered copy.

The .m3u8 file without a number is the last playlist sent by OBS. It has the same content as the playlist with the highest number. Comparing the numbered files in order shows how the media sequence and segment list changed during streaming.

Validate the Data

Check that the playlists and media segments were created correctly. Confirm that every segment named in a .m3u8 file has a matching .ts file, that the media sequence number increases in order, and that each segment duration is correct.

When validating an HLS stream for YouTube, use the YouTube HLS ingestion specification to check playlist tags, segment duration, codecs, and container formats.

Prepare the Environment

1. Install Python

   PushCap is written in Python. Install Python on the PC that will run the server.

2. Install the required packages

   PushCap requires the flask and tornado packages. Install them with the following commands.

   py -m pip install flaskpy -m pip install tornado
3. Create an HTTPS certificate

   HLS does not always require HTTPS, but the YouTube HLS ingest service receives playlists and media segments over HTTPS. OBS also uses HTTPS for this output. Copy the generated cert.pem and key.pem files to the same directory as PushCap.py.

   For an example of creating certificate files, see the guide for applying a private HTTPS certificate to Wowza Streaming Engine.

   cert.pem

   The certificate presented by the HTTPS server

   key.pem

   The private key used with the certificate

Download and Run PushCap

1. Download the code

   Download PushCap.py from the PushCap project on GitHub.

2. Save PushCap.py

   Save PushCap.py in a suitable directory.

3. Run PushCap

   Open a console, move to the directory containing PushCap.py, and run the program. Keep cert.pem and key.pem in the same directory.

When the following message appears, the program is running and ready to receive an HLS stream.

Microsoft Windows [Version 10.0.20348.4052]
(c) Microsoft Corporation. All rights reserved.
D:\HLSWEB>py PushCap.py
Starting PushCap HTTPS server on port 443...
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PushCap is distributed under the BSD 3-Clause License. It may be used, modified, and redistributed in source or binary form under the license terms and copyright notice. The program is provided as is, without warranty, and users are responsible for its use.