This video clip:
https://www.youtube.com/watch?v=wc0PB6Azwn0
What is the max audio bitrate and how to detect real audio bitrate? is it the same? Please no rumors and no guessing.
Does it depend on the video quality I am watching (1080p, 720p, etc)?
If you say - yes, it makes no sense, because the clip was uploaded at one bitrate only.
Hope, someone who knows the subject can answer that questions.
Is it possible to detect the audio bitrate from YouTube video at all?
Stats for nerds is useless, it shows no audio bitrate.
Taking consideration lossy (vs lossless) audio max is 320 Kbps, it cannot be higher than that by definition.
Anyone who knows?
You can use the command line tool youtube-dl to list all available transcodings for a given YouTube video by running youtube-dl -F <url-to-your-video>.
Example output using the URL mentioned in your question:
Studying the output we can see that the audio transcoding with the highest bitrate is "format 251" using the opus codec at an average bitrate of around 145k. Note that YouTube is not using a fixed bitrate but rather a variable bitrate with target of ~160k.
The opus codec is currently supported in most modern browsers (but not Safari). Browsers without support for opus will fallback to the m4a stream at a variable bitrate targeting ~128k.
If you want to make 100% sure which audio transcoding you're currently listening to, you can right click the YouTube video player and select "Stats for nerds" and look for the number mentioned in the codecs section and cross-reference that with the output given by youtube-dl:
Does it depend on the video quality I am watching (1080p, 720p, etc)? If you say - yes, it makes no sense, because the clip was uploaded at one bitrate only.
Yes, it depends on video quality. When you're choosing a video quality, you're not just choosing the video quality... you're choosing the audio quality as well. YouTube isn't giving you the option, but it's part of the package.
Videos aren't served as-is, they're transcoded. You upload your video and it's re-compressed at a variety of different bitrates with different settings.
Your audio bitrate depends on what YouTube decided to encode it as. Each video may have many versions of the stream.
The best thing you can do is get a build of FFmpeg with libquvi enabled, and let it parse the page, find the streams, download the stream, demux, and figure things out for you from there.
Taking consideration lossy (vs lossless) audio max is 320 Kbps, it cannot be higher than that by definition.
Your definition is wrong. There are all kinds of lossy audio codecs, and they can be ran at a variety of bitrates.
Related
I'm studying to collect RTSP stream's video information
Codec, Frame rate, resolution, bitrate, etc.
But i can't find How to get realtime RTSP stream's bitrate.
What is formula of RTSP stream's bitrate??
I googled that. but i can't find it. It was just formula for saved video's bitrate or network bitrate.
please help me
A picture that explains the answer I want
I would like to stream a .avi container and not use any codec in the encoding process, that is, I do not want it to encode in H264 or H265, just upload the video and do not encode it, I am using the Azure SDK media services in .NET.
The presets that azure media services has for example in their sdk, they all use h264 or h265 to encode and return an mp4, I just want to upload .avi and see if it is possible that it does not apply any compression and then download the .avi
Thanks!
Adding the answer here. It looks like you were wanting to do a lossless, or near lossless encoding pass using CRF (constant rate factor encoding). There is currently no support for setting CRF encoding in the standard encoder in AMS, but there is work going on to add CRF encoding settings to the SDK in the near future.
For now, you are limited to the settings available in the Transform preset in the H264 or H265 Layers.
You can see all of the available encoding settings most easily in the REST API
https://github.com/Azure/azure-rest-api-specs/blob/main/specification/mediaservices/resource-manager/Microsoft.Media/stable/2021-06-01/Encoding.json
Or if you look at the Transform object in your favorite SDK. Look at the H264Video and H264 Layer classes in the model, as well as the H265 equivalent ones for settings you can control in your code.
https://learn.microsoft.com/en-us/dotnet/api/microsoft.azure.management.media.models.h264video?view=azure-dotnet
https://learn.microsoft.com/en-us/dotnet/api/microsoft.azure.management.media.models.h264layer?view=azure-dotnet
UPDATE: SDK for .NET is available now with Exposed RateControlMode for H264 encoding, enabling 2 new ratecontrol modes - CBR (Constant Bit Rate) and CRF (Constant Rate Factor).
See- https://www.nuget.org/packages/Microsoft.Azure.Management.Media
I am working on "upload video & audio to server",I want to know which format is best for upload (consider the quality & file-size)
video formats are just containers, if you want to consider quality and file size you should look into the encoding of video. For ios based devices h264 encoder with high efficiency level 4 provides the good compression, hence you will get good quality in less file size.
If you want to learn about conversion of video data from one format to another please look into ffmpeg.
Which video formats can we use in OpenCV? Can anything in addition to AVI and load from camera be used?
If these are the only supported formats, is a video converter required to use other video formats.
I'm not sure how up-to-date it is, but this OpenCV wiki page gives a good overview of what codecs are supported. If looks like AVI is the only format with decent cross-platform support. Your options are either to do the conversion using an external converter (like you suggest) or write code that uses a video library to load the image and create the appropriate cv::Mat or IplImage * header for the data.
Unless you're processing huge quantities of video I suggest taking the path of least resistance and just converting the videos to AVI (see the above link for the details of what OpenCV supports). Just be careful to avoid lossy compression: it will wreck havoc with a lot of image processing algoritms.
OpenCV "farms out" video encoding and decoding to other libraries (e.g., ffmpeg and VFW). Also, have a look at the highgui source directory to see all of the VideoCapture wrappers available (specifically pay attention to the cap_* implementations). AVI is merely a container, and really isn't that critical to what video codecs that OpenCV can read. AVI can contain several different combinations of video, audio, and even subtitle streams. See my other answer about this. Here is also a quick article explaining the differences between containers and codecs.
So, if you're on Linux make sure ffmpeg supports decoding the video codec you are interested in processing. You can check what codecs your version of ffmpeg supports with the following command:
ffmpeg -formats
On Windows, you'll want to make sure you have plenty of codecs available to decode various types of video like the K-Lite Codec Pack.
I am currently in a webcam streaming server project that requires the function of dynamically adjusting the stream's bitrate according to the client's settings (screen sizes, processing power...) or the network bandwidth. The encoder is ffmpeg, since it's free and open sourced, and the codec is MPEG-4 part 2. We use live555 for the server part.
How can I encode MBR MPEG-4 videos using ffmpeg to achieve this?
The multi-bitrate video you are describing is called "Scalable Video Codec". See this wiki link for basic understanding.
Basically, in a scalable video codec, a base layer stream itself has completely decodable; however, additional information is represented in the form of (one or many) enhancement streams. There are couple of techniques to be able to do this including lower/higher resolution, framerate and change in Quantization. The following papers explains in details
of Scalable Video coding for MEPG4 and H.264 respectively. Here is another good paper that explains what you intend to do.
Unfortunately, this is broadly a research topic and till date no open source (ffmpeg and xvid) doesn't support such multi layer encoding. I guess even commercial encoders don't support this as well. This is significantly complex. Probably you can check out if Reference encoder for H.264 supports it.
The alternative (but CPU expensive) way could be transcode in real-time while transmitting the packets. In this case, you should start off with reasonably good quality to start with. If you are using FFMPEG as API, it should not be a problem. Generally multiple resolution could still be a messy but you can keep changing target encoding rate.