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The Sinch SDK will use P2P for the voice stream when possible. The ICE protocol is used for NAT traversal. If a P2P channel is not possible (for example when both sides are behind a symmetric NATs) the voice channel will fall back to Sinch media proxies. Approximately 70-75% of the calls made with the SDK can be expected to go over P2P, while approximately 25-30% of the calls can be expected to go through servers. This is due to firewall restrictions.   Visit the In-App Voice Calling product page to learn more about Sinch’s In-App Voice calling products. ... View more

The bandwidth required varies depending on whether you are making app to app or app to phone calls. But typically: Acceptable bandwidth: > 25 kbps Excellent bandwidth: > 30 kbps   Further Information: Sinch Documentation site - learn how you can leverage the Sinch Voice APIs. SDK - learn how you can leverage the Sinch SDKs to easily enable calling. Visit the In-App Voice Calling product page to learn more about Sinch’s In-App Voice calling products. ... View more

Sinch uses the Opus codec for High-Definition voice. This is a flexible codec which adapts the voice quality to the quality of the network currently used. A good connection results in HD voice quality.   Sinch uses the hardware accelerated H.264 codec for video for both iOS and Android. If this is unavailable, then software H.264 is used.   Visit the In-App Voice Calling product page to learn more about Sinch’s In-App Voice calling products. ... View more

Sinch uses WebRTC, which is an open framework for the web that enables Real Time Communications in the browser. It includes the fundamental building blocks for high-quality communications on the web, such as network, audio and video components used in voice and video chat applications.   Visit the In-App Voice Calling product page to learn more about Sinch’s In-App Voice calling products. ... View more

Yes, you will need credit to call regular phone and PSTN numbers.   You can add credit to your account via a credit card or PayPal in the payment section of the Sinch Customer Dashboard.   Visit the Sinch Voice Calling product page to learn more about Sinch’s Voice products. ... View more

After you have made your first payment using the Sinch Customer Dashboard, you will have the option to use our auto top up feature via PayPal. With auto top up, you can set a credit value to automatically be charged to your PayPal account as soon as your account balance goes under 10% of your defined top-up value.   If you do not want to use this feature, just leave it blank and use the manual top up option. Using manual top up, you can add credit when needed, but if you ran out of credit, your call will not be connected.   If you decide to use the auto Top-up feature, it’s important that you set your top-up quantity to a value that is compatible to your balance burn rate, so you minimize the risk of running out of balance, due to lack of time to process your payment.   For example: Customer (A) initiates 1000k calls per hour, and his burn rate is around 100USD per minute. The top-up value set on his account is 1000USD per auto top-up event, which means that, when his balance < 100USD (10% of 1000USD) Sinch will trigger the Auto top-up. This will give us only 1 minute to successfully process the PayPal debit and credit the 1000USD into their Sinch Balance.   If for some reason this process gets delayed for more than 1 minute. Or the burn rate increases for a short period of time, there is a reasonable risk that the account may run out of “money”.   In this case, to avoid such situation, the top-up value should be set to 2k, maybe 5k USD, which will trigger the top-up action when the balance is 200 or 500USD, giving more time to the process to be successfully completed.   Refer to the Sinch Voice Calling product page to learn more about Sinch’s Voice products and for details of pricing. ... View more

Yes, you can use pre-recorded audio in multiple formats, including WAV and MP3.   Pre-recorded messages can be used on a IVR scenario, when you want to play messages in a menu scenario instead of using TTS, and it can also be used on a callout scenario, when the customer want to trigger a call to a destination number, and play a message directly, such as a PIN code for a OTP (One Time Password) call.   Further Resources: External media support – Content caching, limits, supported Content-Type headers. Text-to-speech Callout - Server initiates a call to a phone number and plays a synthesized text messages or pre-recorded sound files.  Playfiles - Plays Interactive Voice Response (IVR) files for the supported locale at the Sinch backend. An IVR message is played only on the caller’s side. ... View more

Yes, we do support G.711 PCMU.   Visit the Sinch Voice Calling product page to learn more about Sinch’s Voice products. ... View more

Our customers can record all PSTN and SIP and Conference calls.   Further Information: Learn how you can leverage the Sinch API to easily enable voice calling. Visit the Sinch Voice Calling product page to learn more about Sinch’s Voice products. ... View more

Calling Line Identifiers (CLI) can be used in conjunction with a purchased DID (Direct Inward Dialling service) from the Sinch Customer Dashboard to show as an incoming number on a voice call.  If we do not have a DID in your region, then we can acquire one for you. Please get in touch.   Migration of customers' existing DIDs is also an option, please contact Sinch support if that is your case.   App to phone call setting CLI Android SDK iOS SDK Further Resources: SIP calls PSTN calls. ... View more

Yes, it is possible to connect to a conference from different call types, using SVAML (Sinch Voice Application Markup Language) command connectConf in an ICE reply during a call flow or a Conference callout to a PSTN endpoint.   Further Resources: SVAML quick reference Conference Callout quick reference Visit Sinch Developer site to learn more. ... View more

SIP Trunks are an application layer protocol which facilitate two-way conversations or multiple people on a conference call to communicate via audio or video over an IP network.   In Sinch SIP trunking service the incoming call legs and outgoing call legs is to your own SIP infrastructure such as a SIP IP-PBX, SBC or similar equipment.   Using SIP trunking together with Callback API you can combine all different types of incoming calls and outgoing calls the Sinch platform supports, including: Call recording Conference rooms Visit Sinch Developer site to learn more about SIP Trunking. ... View more

Voice gives your users more reasons to engage with your product and enables your users to call mobile and landline phones in 200+ countries, capitalize on growing data plans, and expand your user base.   Voice calling keeps users engaged for longer and enables you to collect call metadata to better understand user behaviour within mobile apps. Other use cases include making calls to your customer support team from within the app or the ability to make calls outside of the app for user acquisition.   Visit the Sinch Voice Calling product page to learn more about Sinch’s Voice products. ... View more

Currently this functionality is unavailable, but is in our roadmap and will be offered as part of our REST APIs in the future.   Logs and voice reports are available however in other methods   DICE event (detailed view) If the application in use has a defined callback endpoint defined on our portal, the calling platform will send an event called DICE at the end of each call, which can be used by the customers to track each single call.   Dashboard logs (https://dashboard.sinch.com/voice/logs) In the dashboard you use to manage your applications and services go to voice and video -> logs.  Here you can filter by Call ID, Application name for up to 7 days previously.   Reports (https://dashboard.sinch.com/voice/reports) Call reports with costs are downloadable for PSTN origination, termination and App termination.   Visit the Sinch Voice Calling product page to learn more about Sinch’s Voice products. ... View more

Login to the Sinch Dashboard - buy numbers, which allows you to easily find voice enable numbers from a wide range of countries.     If you do not already have an account for the Sinch Customer Dashboard sign up now.   Note: Some countries require local entities/presence in the country and additional company information before we can source you a number.   If you are interested in our Voice services or have any further questions, contact Sinch. ... View more