fre:ac is a free audio converter and CD ripper with support for various popular formats and encoders. It converts freely between MP3, M4A/AAC, FLAC, WMA, Opus, Ogg Vorbis, Speex, Monkey's Audio (APE), WavPack, WAV and other formats.
Since audios are used in various systems and places, therefore these come in various formats suitable for each system. For instance, a song file will have different format than a voice -note on a messenger such as Telegram or WhatsApp. But there are times when we needed to convert an audio file from one format to another, or even to same format but different attributes. There can be multiple reasons of doing so, such as a voice note having opus format is not playing in a music player, so why not convert it into MP3.
1st mass mailer serial. Free Audio Converter from DVDVideoSoft allows you to convert audio files to different output formats so that you can play them through various devices and programs. You have the option to convert the files to MP3, M4A, FLAC, ALAC, AMR, WAV, WMA, and more, as well as being able to select the output quality with options including: Original, LAME Insane, LAME Extreme, LAME Standard, High Quality, and Old Standard.
Note that because of the removal of certificate store hooksin openssl 1.1.1 and later, there are unfortunately nosupported versions of that library which can be used withthe code in opusurl to validate https responses againstthe system certificate store on Windows. Using the systemdefault access to the certificate store on other platformsworks fine.
The opus encoder and decoder do not need to have matched sampling rates or channel counts. It is recommended to always just decode at the highest rate the hardware supports (e.g. 48kHz stereo) so the user gets the full quality of whatever the far end is sending.
If libopus is built with -DNONTHREADSAFE_PSEUDOSTACK (instead of VAR_ARRAYS, or USE_ALLOCA), it will use a user-provided block of heap instead of stack for many things, resulting in much lower stack usage.This makes the resulting library non-threadsafe and is not recommended on anything except limited embedded platforms.
Computing the duration directly from the file contents allows files to be written in a single pass, without any seeking, which is necessary for live streaming. Chaining also simplifies live streaming, as you can just pipe multiple files into the same network connection, with all associated metadata updates, etc., and the results are still valid .opus files (contrast with the hacks used to add metadata to MP3 streams).
Opening a typical .opus file, which is not multiplexed and not chained, and computing the duration over the network requires just one extra HTTP request, which can proceed in parallel with the buffering in the main request. This is the behavior you will get from libopusfile's HTTP backend by default.
Enumeration of chain boundaries can be expensive in files with many links, but in our testing libopusfile used nearly an order of magnitude fewer seeks to do this than some other media frameworks (at the time). Storing a duration in a header wouldn't solve this, since every link in a chain has its own, independent headers. If the cost of chain enumeration is a problem, the best way to avoid it is to store the links in separate files (i.e., don't use chaining).
libopusfile includes fallbacks to prevent pathological worst-case behavior when its guesses are repeatedly wrong. Weighted bisection can degrade to a linear scan, but libopusfile's worst case is within a constant factor of naive bisection (i.e., logarithmic). We have only ever observed such pathological behavior in files we manually constructed to trigger it.
libopusfile also takes shortcuts when the target location is near the current position, to make small seeks cheaper. In the best case it can loop forever over very short files whose data is contained in a single page (e.g., less than 1 second long with default encoder settings) without any seeking at all.
As with file durations, an index at the beginning of the file is incompatible with live streaming. It also means more data has to be fetched before a file can start playing over the network, because you must read past the index even when you don't intend to seek. The index could be stored at the end (which even still allows encoding the file in a single pass), but this requires one (or more) extra seeks to read the index (especially if its exact location at the end is not known), either on file open or on first seek. Unlike the final timestamp, which is small and fixed in size, an index grows with the file duration, and can have unbounded size. It is also easy for an index to become out of sync with a file that has been edited or damaged, in which case seeking will simply fail. By contrast, you can seek in a truncated .opus download without issues.
In practice, bisection seeking on VBR audio achieves performance that is very nearly as good as seeking with an index, without any of the drawbacks of an index. libopusfile provides a test program called seeking_example which can be used to benchmark the performance on your files.
As an open format standardized through RFC 6716, a reference implementation called libopus is available under the New BSD License. The reference has both fixed-point and floating-point optimizations for low- and high-end devices, with SIMD optimizations on platforms that support them. All known software patents that cover Opus are licensed under royalty-free terms. Opus is widely used as the voice over IP (VoIP) codec in applications such as Discord, WhatsApp, and the PlayStation 4.
Opus packets are not self-delimiting, but are designed to be used inside a container of some sort which supplies the decoder with each packet's length. Opus was originally specified for encapsulation in Ogg containers, specified as audio/ogg; codecs=opus, and for Ogg Opus files the .opus filename extension is recommended. Opus streams are also supported in Matroska, WebM, MPEG-TS, and MP4.
In November 2011, the working group issued the last call for changes on the bitstream format. The bitstream has been frozen since January 8, 2012. On July 2, 2012, Opus was approved by the IETF for standardization. The reference software entered release candidate state on August 8, 2012. The final specification was released as RFC 6716 on September 10, 2012. and versions 1.0 and 1.0.1 of the reference implementation libopus were released the day after.
On December 5, 2013, libopus 1.1 was released, incorporating overall speed improvements and significant encoder quality improvements: Tonality estimation boosts bitrate and quality for previously problematic samples, like harpsichords; automated speech/music detection improves quality in mixed audio; mid-side stereo reduces the bitrate needs of many songs; band precision boosting for improved transients; and DC rejection below 3 Hz. Two new VBR modes were added: unconstrained for more consistent quality, and temporal VBR that boosts louder frames and generally improves quality.
libopus 1.1.1 was released on November 26, 2015, and 1.1.2 on January 12, 2016, both adding speed optimizations and bug fixes. July 15, 2016 saw the release of version 1.1.3 and includes bug fixes, optimizations, documentation updates and experimental Ambisonics work.
libopus 1.2 Beta was released on May 24, 2017. libopus 1.2 was released on June 20, 2017. Improvements brought in 1.2 allow it to create fullband music at bit rates as low as 32 kbit/s, and wideband speech at just 12 kbit/s.
libopus 1.3.1 was released on April 12, 2019. This Opus 1.3.1 minor release fixes an issue with the analysis on files with digital silence (all zeros), especially on x87 builds (mostly affects 32-bit builds). It also includes two new features:
RFC 6716 contains a complete source code for an older version of the reference implementation written in C. RFC 8251 contains errata. Libopus is the more up-to-date but non-normative branch of the reference implementation.
The libopus reference library has been ported to both C# and Java as part of a project called Concentus. These ports sacrifice performance for the sake of being easily integrated into cross-platform applications.
Google added native support for Opus audio playback in Android 5.0 "Lollipop". However, it was limited to Opus audio encapsulated in Matroska and WebM containers, such as .mkv, .mka and .webm files. Android 7.0 "Nougat" introduced support for Opus audio encapsulated in Ogg containers. Android 10 finally added native support for .opus extensions.
On Windows 10, version 1607, Microsoft provided native support for Opus audio encapsulated in Matroska and WebM containers. On version 1709, support for Opus audio encapsulated in Ogg containers was made available through a pre-installed add-on called Web Media Extensions. On Windows 10 version 1903, native support for the .opus extension was added. On Windows 8.1 and older, third-party decoders, such as LAV Filters, are available to provide support for the format.
Due to its abilities, Opus gained early interest from voice over IP (VoIP) software vendors. Several SIP clients, including Acrobits Softphone, CSipSimple (via additional plug-in), Empathy (via GStreamer), Jitsi, Tuenti, Line2 (currently only on iOS), Linphone, Phoner and PhonerLite, SFLphone, Telephone, Mumble, Discord and TeamSpeak 3 voice chat software also support Opus. TrueConf supports Opus in its VoIP products. Asterisk lacked builtin Opus support for legal reasons, but a third-party patch was available for download and official support via a binary blob was added in September 2016. Tox P2P videoconferencing software uses Opus exclusively. Classified-ads distributed messaging app sends raw opus frames inside TLS socket in its VoIP implementation. 2b1af7f3a8