MPV¶

MPV stream recording has the following characteristics:

•

it is considered an experimental feature by the MPV developers.

Radio streaming uses well known and established codecs (mainly mp3 and aac) and I have had no broken recording while testing the feature (even with flac stations).

•

MPV has the ability to play and record a stream at the same time (both the recorder and the monitor components are active simultaneously).

This is very convenient, since all one has to do is add a command line parameter and start recording, while listening to what’s being recorded.

•

adjusting the volume or muting the player will not affect what’s being recorded.

•

when paused, the player will pause the playback but will keep recording the stream. Furthermore, song titles will stop being updated, but will be correctly displayed and updated when playback is resumed.

MPlayer¶

MPlayer stream recording has the following characteristics:

•

it does not have the ability to record and play a stream at the same time.

This means that the front end (pyradio) will have to use two mplayer instances (execute mplayer twice): one as a recorder and one as a monitor.

•

the recorder will display the song titles in addition to saving the output file.

•

the monitor will be started after the output file gets to a certain size, set to 12000 bytes by trial and error.

•

pausing and resuming the monitor for long will lead to song titles being out of sync, since the recorder will keep receiving data (and song titles) even when the playback if off.

VLC¶

VLC stream recording has the following characteristics:

•

it does not have the ability to record and play a stream at the same time.

This means that the front end (pyradio) will have to use two vlc instances (execute vlc twice): one as a recorder and one as a monitor.

•

the recorder will display the song titles in addition to saving the output file.

•

the monitor will be started after the output file gets to a certain size, set to 120000 bytes by trial and error.

•

pausing and resuming the monitor for long will lead to song titles being out of sync, since the recorder will keep receiving data (and song titles) even when the playback if off.

Recording implementation¶

The following keys are used for this feature:

In order to record a station, recording has to be enabled beforehand, by pressing the “pipe symbol” or “vetical line” (“|”). Then an info message appears, which can be seen here:

https://members.hellug.gr/sng/pyradio/pyradio-recording1.jpg

When this is done an “[r]” will be displayed at the top left corner of the window. This means that recording is enabled, but pyradio is not currently recording to a file.

When playback is started (i.e. start playing a station), an “R” will be displayed at the top left corner of the window (replacing the “[r]” that was already there), which means that pyradio is actually recording the station to a file.

The following image is a mockup presenting the difference.

https://members.hellug.gr/sng/pyradio/pyradio-recording2.jpg

Pressing the “pipe symbol” or “vetical line” (“|”) again will disable recording and nothing will be displayed at the top left corner of the window. The actual recording of the station will still be active, until the station is stopped.

It must be made clear that toggling the recording status for pyradio will actually take effect after a station has been started or stopped. This is because of the way the players get the recording command; through command line arguments, which can only be passed when the player is executed.

Starting recording from the command line¶

One can use the “–record” command line parameter to start the program in recording mode.

This would be extra useful to start playback and recording, for example:

pyradio -p 3 --record

This command would open the default playlist (or the one last used, if set in the config), using the default player, and start playing and recording station No 3.

Note

If the default player is VLC on Windows, and the “–record” command line parameter is used, a message informing the user that recording is not supported, will be displayed.

File location¶

Files created by the recording feature will be saved under the “recordings” folder inside pyradio’s configuration directory.

The file will be named:

[date] [Station Name].mkv

File type¶

pyradio will produce a mkv file when recording a station.

This is just a measure of convenience since the type of audio (mp3, aac, aac+, flac, etc.) the station will broadcast cannot be known beforehand (before starting the recording, that is).

Although a mkv file is a video/audio/subs etc. container, it’s perfectly fine to contain just a sound stream, as is the case of the files produced by pyradio.

The file can be (hopefully) reproduced using any video media player.

Chapters¶

As a convenience, pyradio will write chapter markers to the file produced, provided that:

1.

MKVToolNix (https://mkvtoolnix.download/) is installed.

MKVToolNix is a set of tools to create, alter and inspect Matroska (http://www.matroska.org/) files under Linux, other Unices and Windows.

pyradio uses mkvmerge (mkvmerge.exe on Windows) to add chapters to the MKV file.

2.

The stations will provide ICY Titles (the titles will be used as chapter titles).

Things to consider:

•

The first chaprer will always be at 00:00 and will be the name of the station.

•

Chapters markers timing depends on the time the ICY Titles are received, plus any overhead added by pyradio.

This means that, for whatever reason, a chapter marker may not exactly point to the beginning of the song associated with it.

Cover image¶

PyRadio will insert a cover image to every recorded file when MKVToolNix has been detected.

The default image is named “cover.png” and is located in the “data” folder, within the configuration directory.

There are two way to change this cover image:

1.

To permanently change the cover image for all recordings, create a PNG file named “user-cover.png” in the “data” folder withing the configuration directory.

2.

After you have stopped the recording, set any PNG file as a cover image for the recorded file, using the procedure explained in section Changing the cover.

The image below shows how a chapter aware player will display and handle chapter markers found in a MKV file. The file also uses the default cover image.. This is the Media Player Classic (https://sourceforge.net/projects/mpc-hc/) on Windows 7.

https://members.hellug.gr/sng/pyradio/pyradio-chapters.gif

Linux¶

On Linux you will have no problem installing the package; all distros will include it, either as mkvtoolnix, or mkvtoolnix-cli or whatever.

Just make sure that after the installation you can execute mkvmerge from a terminal.

MacOS¶

On MacOS, it all depends on your System Version, i guess.

First try to use HomeBrew (https://brew.sh/):

brew install mkvtoolnix

I do not know if using HomeBrew for the installation will place mkvmerge into your PATH, but if it does, you are done.

I was not able to install it on Catalina using HomeBrew, so I ended up using the AppImage from MKVToolNix (https://mkvtoolnix.download/downloads.html#macosx). Just make sure you download the right version for your system.

Then, since the installed application was not in the PATH (so that pyradio finds mkvmerge), I just executed (in a terminal):

sudo find / -name mkvmerge

and ended up with

/System/Volumes/Data/Applications/MKVToolNix-54.0.0.app/Contents/MacOS/mkvmerge
/Applications/MKVToolNix-54.0.0.app/Contents/MacOS/mkvmerge

Since I do not know the difference between the first and second result, I will just use the second one, just because it is shorter :)

So, finally:

mkdir -p ~/.config/pyradio/data
echo '#!/bin/bash' > ~/.config/pyradio/data/mkvmerge
echo '/Applications/MKVToolNix-54.0.0.app/Contents/MacOS/mkvmerge  "$@"' >> ~/.config/pyradio/data/mkvmerge
chmod +x ~/.config/pyradio/data/mkvmerge

Files location¶

The file produced by the recording function will be placed in the recordings directory, inside the configuration directory.

If MKVToolNix is not installed, the file will be downloaded in this directory and will not be altered by pyradio.

If MKVToolNix is installed, a “tmp_” prefix will be added to the recorded filename, which will be removed after chapters addition.

Pausing playback¶

After you have started recording a station, pyradio will connect to it and start downloading the station data and at the same time will produce sound for you to hear what’s downloaded.

You can then press “Space” to pause the playback, but still continue downloading the station’s data.

Pressing “Space” again will resume playback from where it left off.

As a consequence, listening to the end of a show that you have paused for say 10 minutes, and then stopping the station (both playback and recording), the file recorded will have an excess of 10 minutes of data, past the end of the actual show.

Finally, please keep in mind that all other keys relevant to starting, stopping and restarting a station’s playback remain the same; only the behavior of the “Space” key has changed when recording is on.

Changing the cover¶

As already stated, PyRadio will embed a cover to every recording (provided that MKVToolNix (https://mkvtoolnix.download/) is installed).

The default image is a PNG file named “cover.png” located under the data folder in the configuration directory.

One can change this cover image using the following command:

pyradio -mkv recorded.mkv -scv image.png

Both recorded.mkv and image.png can be inserted either as an absolute path/filename or as a relative one. In the later case, the relevant file can either be in the current directory or under the “recordings” folder.

Correcting chapter markers¶

PyRadio does provide a way to correct these misplaced chapter markers.

The way to do it is:

1.

extract a SRT file from a recorded MKV file, containing the chapter names as subtitles.

2.

edit the SRT file and correctly place the subtitles.

3.

insert the SRT file to the original MKV file, transforming the subtitles timing and test to chapters.

The following image shows this procedure.

https://members.hellug.gr/sng/pyradio/mkv-srt-to-chapters.png

In detail:

1. Extract the SRT

2. Edit the SRT file

3. SRT to Chapters

Listing recordings and the -mkv command line option¶

The -mkv command line option used above, will specify the MKV file to use with subsequent commands, but there is a problem here; recorded file names are too complicated to pass as arguments, written by hand or otherwise.

PyRadio addresses this issue by accepting a number instead of a file name as a parameter to **-mkv*; this number is actually the index of the required file in the alphabetically sorted list of existing files.

To get the index number, one would just use the -lr command line option:

$ pyradio -lr
List of files under recordings
┏━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ # ┃ Name                                                    ┃
┡━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ 1 │ 2023-11-02 17-06-03 Lounge (Illinois Street Lounge).mkv │
│ 2 │ 2023-11-02 14-37-17 Pop (PopTron! - SomaFM).mkv         │
│ 3 │ 2023-10-31 20-15-41 ΕΡΑ - Κέρκυρα (Περιφερειακός).mkv   │
│ 4 │ 2023-10-31 15-22-57 Celtic Sounds.mkv                   │
│ 5 │ 2023-10-31 11-14-43 La Top - 107.7 FM.mkv               │
└───┴─────────────────────────────────────────────────────────┘
    

This way, the command:

pyradio -mkv \
'2023-11-02 17-06-03 Lounge (Illinois Street Lounge).mkv' -srt

could actually be inserted as

pyradio -mkv 1 -srt

In this case, 1 is the index of the file in the list provided by the -lr command.

As a convenience, negative numbers can also be used; -1 means the last file, -2 the second from last, etc. This way, to work with the last recorded file, one would just use “-mkv -1” on all the necessary commands.