Bluetooth Media Control and display

[DavidM42]

So first of all thanks for this really cool project.
The only two things I'm still missing from this is the possibility to skip songs/pause on a bt client player device (like a phone) and the forwarding of the currently playing track into rds.
I've done some reasearch because I'd like to help integrating them via PR but I don't understand the project enough for now.
The thing needed for this is probably the AVCRP protocol to control media playback and get more info from apps integrating into this protocol on phones. I found out that you can access this information/send info to bluez via the dbus but I could not get it done myself (partly because of bluez documentation beeing sparse). Does anybody know more about this topic?

[DavidM42]

Update

I found some resources for what to do with the bluetooth stack:

1. This SO question with example code to get currently playing music metadata
2. This reddit question with the interesting part in edit 2 and following

Getting data about playback

import dbus
#XX_XX_XX_XX_XX_XX is a placeholder for bt mac adress of connected device

#probs dict should yield same results as terminal command but in more structured format
#qdbus --system org.bluez /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/player0 

bus  = dbus.SystemBus()

player = bus.get_object("org.bluez", "/org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/player0")
BT_Media_iface = dbus.Interface(player, dbus_interface="org.bluez.MediaPlayer1")

BT_Media_probs = dbus.Interface(player, "org.freedesktop.DBus.Properties")

probs = BT_Media_probs.GetAll("org.bluez.MediaPlayer1")
print(probs)

Control Playback

And this command for skipping the current song

dbus-send --system --type=method_call --dest=org.bluez /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/player0 org.bluez.MediaPlayer1.Next

The last word in the value can be:

• Next
• Pause
• Play
• Previous
• Repeat
• FastForward
• Rewind
• Stop

as found in the reddit question.

I'm not that familiar with dbus so I couldn't figure out yet how to send the commands with the python library.

Now the thing I'm unsure with is how to integrate the metadata into the extisting rds services and the commands into the button service to use when BT is connected.

[DavidM42]

also just saw #29 . info here should help with this issue

[morrolinux]

Hello! First of all, thanks for your interest, second, there are so many good informations here, I'll have to read through them carefully when I get a slot of free time. Also, I wouldn't worry too much about integrations if I were in you, because I've got a good news as well: I'm thinking about re-writing the whole project in python, it would be much easier to integrate, and right now the project suffers from a variety of reliability inconsistencies when it comes to bluetooth audio playback (for some works, for others don't) probably due to it relying on system and bash scripts for detecting new devices upon connection.
You want to help, you're very welcome! I'd suggest you to improve your python3 because we'll probably need it soon :)

[DavidM42]

That's some good news as python is my preferred language. I'd like to help as far as I can. Do you have any plan when you want to start the rewrite?

[DavidM42]

I got a working script to control BT media playback. It does not do anything for local playback as I only use bluetooth but it seems to work.
I replaced the mpradio-pushbutton-skip.py in my local /bin/ folder with mine to utilize the existing service.

How to use

• Normal click: Play/Pause
• Double click: Skip track to next
• Triple click: Previous track/back to start of track
• Hold button for 5 seconds: Shutdown pi

Code

import RPi.GPIO as GPIO
import time
from subprocess import check_output, call
import re

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def get_mac():
	device_cmd = "bt-device -l"
	result = check_output(device_cmd, shell=True)
	regex = "[(].*[)]"
	mac = re.findall(regex, result)[0]
	#print(mac)
	return mac.replace(":","_").replace("(","").replace(")","")

#TODO refactor for less code repetition to just alter print and last command

last_play = True

def pause():
	cmd_arr = ["dbus-send", "--system" , "--type=method_call", "--dest=org.bluez", "/org/bluez/hci0/dev_" + get_mac() + "/player0", "org.bluez.MediaPlayer1.Pause"]
	global last_play
	if last_play == False:
		print("Play")
		cmd_arr[5] = "org.bluez.MediaPlayer1.Play"
	else:
		print("Pause")
	#inverse last play after command
	last_play = not last_play
	call(cmd_arr)

def skip():
	print("skip")
	global last_play
	last_play = True
	cmd_arr = ["dbus-send", "--system" , "--type=method_call", "--dest=org.bluez", "/org/bluez/hci0/dev_" + get_mac() + "/player0", "org.bluez.MediaPlayer1.Next"]
	call(cmd_arr)

def previous():
	print("previous")
	#spotify start playing on previous command so removed
	#global last_play
	#last_play = True
	cmd_arr = ["dbus-send", "--system" , "--type=method_call", "--dest=org.bluez", "/org/bluez/hci0/dev_" + get_mac() + "/player0", "org.bluez.MediaPlayer1.Previous"]
	call(cmd_arr)

def shutdown():
	print('shutdown')
	call(["killall", "mpradio"])
	call(["killall", "sox"])
	call(["shutdown", "-h", "now"])
	time.sleep(10)


state = True
max_delay = 1
shutdown_push_time = 5
last_time = time.time()
pulse_count = 0

while True:
	new_state = GPIO.input(18)

	if new_state == False and state == False and (time.time() - last_time) > shutdown_push_time:
		#if button is still pressed after 5 seconds shutdown device
		shutdown()

	if new_state == False and state == True: #going from off to on
		pulse_count += 1
		state = new_state
		last_time = time.time()

	elif new_state and state == False: #on to off
		state = True

	if time.time() > (last_time + max_delay) and pulse_count > 0: #too long a delay so after end of sequence
		if pulse_count == 1:
			pause()
		elif pulse_count == 2:
			skip()
		elif pulse_count == 3:
			previous()
		else:
			pause()
		pulse_count = 0

[morrolinux]

@DavidM42 I can't make precise schedule at the moment because everything's so "dynamic" in this period, but I probably would start with the bluetooth a2dp part to see if it makes sense.

[morrolinux]

So I've been laying down some "projectual ideas" and I think I'm going for this logic

In python we can easily popen processes and attach to their stdin/stdout so I think it will also be possible to hotswap sources (players) and sinks (outputs) without having to restart

[DavidM42]

Nice. Seems good. pi_fm_adv should be the go to. From my testing it produces much better quality than the other driver.
I still have a question regarding the "old" current implementation. How is the rds input handled? I'd like to write a test script to pipe Bluetooth song info into rds but I couldn't figure out the correct way.

[morrolinux]

@DavidM42 have a look at mpradio-legacyRDS.sh , but basically it's a matter of piping your text like so: echo "PS $legacytitle" >/home/pi/rds_ctl
and pi_fm_adv reads polls the control pipe. more info about that in its repo

[Hurricos]

It's been a while since I've poked around on this, but I think I'll throw my hat into the ring this weekend. I am not the strongest Python coder, but I love the ideas you put together in that diagram @morrolinux, so I should be able to help cobble something together if you want to cooperate on a python branch.

Python also means we can rely on stronger id3 libraries. I'm quite excited to figure out how to interface with stdin/stdout of processes via popen.

[Hurricos]

@DavidM42 nice discoveries RE: AVRCP! I'd tried but failed to scratch that itch a while ago :( I'll see what I can do to help now :)

[morrolinux]

@Hurricos Cool! since the last schematic I've changed the design just a bit on the remote controller part, but overall that's the thing. I'll update the schematic soon. This afternoon I'm going to open a new repo on github to share the current progress. (spoiler: core functionalities are already working!) :)

[morrolinux]

@Hurricos I've published a new repo for the python version here
I'm currently putting the basis for a media indexer to feed to the playlist manager, I'll create an ad-hoc data structure and I'd like you to take care of the id3 stuff and filling-in the data structure with those data. just tell me if/when you start working on something, so that we can coordinate better

[morrolinux]

@DavidM42 same for you of course :)

[DavidM42]

I've got a few questions about the rewrite.

• Which python version is the minimum supported?
• Any requirements concerning additional python libraries? License wise restricted, maybe as few dependancies as possible or whatever?
• Could you explain how to setup a usable dev environment. So linux of course but any other reccomendations?

And concerning bluetooth rds I'm facing a bit of a non technical problem. I couldn't find any radio which has rds info besides the car but I won't be debugging on a pi in a car :D