The popularity of live broadcasts is not diminishing, and many people are also involved in it, but everyone does not know much about the software development of live broadcast platforms. In the live broadcast platform, the use of audio and video technology is essential to ensure the clear and smooth live video images. Today, let’s take a look at the general process of audio and video technology processing.
Audio and video technology mainly refers to audio technology and video technology. The processing process of the two in live broadcast is similar, and they are generally divided into five major steps: data collection, encoding, transmission, decoding and rendering.
Live broadcast platform software development, data collection
Data collection is the first step in the video streaming process. The basic equipment of the system obtains the original video data and outputs it to the next link.
1. Data collection classification
Video collection is divided into two different data collection methods: audio collection and image collection, and the corresponding input sources and data formats are completely different.
2. Audio collection
Audio data refers to the collection of external sounds, either in pure audio mode or combined with images. The audio collection process is mainly to collect the signals in the environment into PCM encoded raw data through the equipment, and then encode and compress the data into MP3 and other formats for distribution. Common audio compression formats are: MP3, AAC, OGG, WMA, Opus, FLAC, APE, m4a and AMR.
3. Image acquisition
Image data is a continuous animation that combines pictures into one or more groups to form a video that can be viewed with the naked eye. The image acquisition process is mainly taken by cameras and other equipment into YUV-encoded raw data, and then encoded and compressed into H.264 and other format data for distribution. Common video packaging formats are: MP4, 3GP, AVI, MKV, WMV, MPG, VOB, FLV, SWF, MOV, RMVB and WebM.
Live broadcast platform software development, audio and video encoding and decoding technology
In fact, video encoding and decoding are implemented in accordance with a certain algorithm, which is also an encoding and decoding algorithm for the analysis of audio and video information. However, audio algorithms are diverse and more complex than video. And different scenes need to choose different audio decoders.
There are three commonly used implementation schemes for audio coding and decoding: the first is to use a dedicated audio chip to collect and process voice signals, and the audio coding and decoding algorithms are integrated in the hardware. The second solution is to use an A/D capture card plus a computer to form a hardware platform, and the audio codec algorithm is implemented by computer software; the third solution is to use a high-precision, high-speed A/D capture chip to complete the voice signal collection.
Live broadcast platform software development, content distribution and transcoding of audio and video streams
1. Front-end equipment, mobile phones or cameras collect and process the live audio and video content before pushing it to the platform origin server (using multi-machine cluster hot backup mechanism).
2. The origin server is generally connected to a professional disk array storage device. When the origin server receives the data, it will first copy multiple copies and forward it to each CDN node below, and then copy one copy and send it to the transcoding server. The transcoding server will transcode each audio and video stream received in real time. The transcoding server will save the real-time live stream recording to the disk array for the convenience of users for playback.
3. Since audio and video content needs to be completed by a high-performance server, in the process of real-time transcoding, there are often problems that cannot meet the requirements due to improper considerations. After all, the current live broadcast application belongs to a large-scale live broadcast operation with high concurrency. At different time periods in each live broadcast room, hundreds or even thousands of live streams will be transcoded in real time. As a result, more high-configuration servers need to be configured, and the cost will increase relatively.
4. The transcoding of live streams must be real-time, and the transcoding delay must be within 1s. There is still a certain gap to the previous 2-3s delay. Therefore, in order to ensure that the audio and video transcoding can proceed smoothly after the development of the live broadcast software is completed, it is not only necessary to work hard on the configuration of the server, but also to pay attention to whether it has a high degree of real-time performance and whether the transcoding delay can be controlled within a certain time Inside.
The above content is just a general process concept, and more practical problems will be encountered in specific implementation. After all, the development of live broadcast platform software requires comprehensive technical reserves and rich practical experience.