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14

Short answer: Blocks are units for inter-frame comparison; Prediction is based on amount of blocks presenting on both previous and following images; Longer answer: As input, a video encoder receives nothing else but a sequence of frames. In most cases, the adjacent frames are very similar to each other, and the encoder attempts to figure out whether these ...


13

240P, 480P, 720P, etc. give you vertical resolution. However "P" does not stand for "pixels" but for "progressive". 720p means that all 720 lines are drawn in each frame. It is the opposite to Interlaced (denoted as "i") where just half of the lines is drawn each frame. So the numbers give you vertical resolutions. Horizontal resolution depends on a given ...


7

Parsing a complete digital film is an immensely complex task. Because you mostly ask about WebM – a container format – I’ll concentrate on that. You always start with individual streams containing the payload data: video (e.g. H.264, VP9), audio (e.g. AAC, Opus) and subtitles (e.g. SubRip, Blu-ray PGS). Tied to those streams is some metadata needed for ...


6

720P 720 means 720 lines to paint, the image on the screen has this amont of lines. P means full pictures, so every line is painted, to create a image on the screen. If you have a 100Hz device, the device paints 100 full pictures in 1 second. All 720 lines are painted each turn. You can not find out the resolution by this information.


6

Unless your subtitles overlap, the algorithm is pretty simple: keep the subtitles in an ordered list. in your event loop, determine the current time if it is larger than the end time of the current subtitle, unpost it if it is larger than the start of the first subtitle in the list, post it and remove it from the list. Do you expect anything more ...


5

Video container formats are typically made up of a series of content blocks. A block typically consists of a few marker bytes (important for finding the next block if you get incomplete data while streaming), a type code (metadata, audio data, video data, ...), a length, followed by some amount of data. The file would typically start with a metadata block. ...


5

This is highly subjective based on the person. I'm an intuitive learner, I have to stick my hands into something and wiggle them about, get cut and bit to learn. So I go straight to the documentation to find the knobs and wheelies I can turn. But for many, this method is as good as tea leaves. I think based on the way education systems tend to teach people ...


4

VDPAU only accelerates the decoding/playing of video. I don't know if the time taken to copy the raw video to the GPU encode, and then read back the compressed data would really mean there was much benefit from a GPU. With playback you are forced to copy the data to the GPU anyway and it's obvisuly better to copy the smaller compressed source stream. There ...


4

The main issue I have here is are the 720P, 480P, 240P... classes for defining video quality or do they unambiguously define the resolution of the video? If you have a video file, and all you know is that it's 1080p then it's safe to assume it's 1920x1080. The 1080p and 720p formats are often 16:9 aspect ratio. If you have a video file, and all you know is ...


4

Subtitles are ordered: the ones which appear later in the video are stored after the ones which appear earlier. Therefore, use a simple cursor which points to the next subtitle to show. In order to make the subtitles disappear (while ensuring that overlapping is possible), either set individual timeouts for every subtitle being shown, or use a second ...


3

Your question is valid and theoretically I think you can use Progressive Downloads for live video streaming. Actually A lot of Online Streaming Video like YouTube etc already use HTTP. I am assuming you are strictly talking about LIVE streaming and not just streaming. You will have to implement the Live Streaming use cases though, yourself! Which otherwise ...


3

Presumably you're talking about MPEG compression, or some variant such as MPEG 4 part 10 (aka H.264). In this case, prediction in a B-frame doesn't just choose the better of a preceding or following frame. Rather, it does a linear interpolation between blocks from the two frames, then encodes the difference from that. You frequently see relatively linear ...


3

I'm not aware of any completely automatic software solution, but this Paper (SyncTS: Automatic synchronization of speech and text documents) gives a possible approach. ABSTRACT In this paper, we present an automatic approach for aligning speech signals to corresponding text documents. For this sake, we propose to first use text-to-speech synthesis (TTS) to ...


3

I am afraid that's not possible. This is how transparency is calculated when two objects overlay: http://en.wikipedia.org/wiki/Alpha_compositing One of the objects must have an opacity of 1 if you don't want the overlay area to be seen through.


2

I think it's always good to have a 'look at the puppy' type presentation for mobile stuff. Why not a simple app that shows off communication? Chinese whispers, peering from app/os to app/os.... Any fancy throw accelerator craftsmanship the better, and of course make it funny. Wins over any social media app for me.


2

It is possible and it has been already done decades ago. Currently only challenge is to streamline it sufficiently to be run on mobile devices. Examples http://www.youtube.com/watch?v=PrzjLg4voEM http://www.youtube.com/watch?v=k-wOJ8rFy8Q Currently that kind of result can be achieved with off-the-shelf open source libraries such as OpenCV. In fact ...


2

Subtitle files typically holds textual data, but there's no reason why you can't use it to associate arbitrary data or a reference to the data (if the actual data is too long for convenience). Note that subtitle files are usually time based rather than frame based. If it's crucial for your app that the data are associated with precise frames, you'll need to ...


2

Your DRM scheme is based on security by obscurity. It won't take long until people figure out that your custom video format is just a zip-archive and will extract it with 7zip to get the actual file. You could make it a bit harder by encrypting it, but people will also be able to figure these out and obtain your decryption key by reverse-engineering your ...


2

Does this mean I should learn OpenCV in another language first in order to utilize it in Swift? Yes, you should learn it in the context of its native C++, because the value of OpenCV doesn't have much to do with C++, or any programming language, the value is in the mathematical tools it provides. OpenCV at its heart is a toolkit of mathematical functions. ...


1

The client and server share responsibility if you're using HTTP requests for partial content: Whenever the client sends a partial GET request with a Range request header to the server, then server should intercept on the conditional GET request headers (all headers starting with If) and handle accordingly. Whenever the If-Match or If-Unmodified-Since ...


1

A video is a sequence of framed images that are displayed at a rate one after another. If we had all frames of a video clip in our browser, we could display them one after another at a frame rate and there we had our video playing! This sounds like a plan, let us see how we can translate this into an actual web application. From what we planned, we divide ...


1

billions of websites are using various techniques for streaming their videos to fit the user needs (Internet connection, browser, OS version) are playing a vital role for which technique the server will try to use. Despite I've made a complete video conference that is working using OpenTok, I am not sure how it works with AJAX Requests, also please note ...


1

What you're seeing in the line of code <source src="@Url.Content(Model.tbl_Video.VideoPath)" type='video/mp4' /> is just ASP.NET MVC's way to insert the correct source element into a <video> tag. ASP.NET MVC has no responsibility whatsoever in the streaming process. The browser streams the video content directly. Further Reading HTML <...


1

In response to that last comment of yours, someone has actually coined this difficulty as the "Analog Hole". You cannot simultaneously show something to a user, and hide it from their computer's access. http://en.wikipedia.org/wiki/Analog_hole It still might be possible to A) Provide basic download difficulties to at least make it very difficult for the ...


1

This needs clarifying. Clime is correct in this answer. The P in 1080p 720p refers to 'progressive'. It means that the image is intended to be render its lines to screen one line at a time, sequentially. This comes from the old days where TV was a cathode-ray tube device that needed to render images in an interlaced manner to improve the temporal ...


1

What you need to do is to read over the license itself to understand more. In order to help you though, here is a short excerpt from Wikipedia: "The MIT License is a free software license originating at the Massachusetts Institute of Technology (MIT). It is a permissive free software license, meaning that it permits reuse within proprietary ...


1

Absolutely this is possible. MathWorks has a Matlab toolbox for doing the basics of recognizing people. Noticing red clothing or height over 6'0" will require you to do some more work. What's amazing to me is that this kind of thing can be done on a good PC these days.


1

No. That method will generally yield very erroneous (low) results. Video codecs generally do a LOT of compression on the video stream, as part of encoding the video. The bit rate is of the bits AFTER encoding.


1

There are various theories about how people learn. On the other hand, most programmers have some things in common: We generally don't have much time, and we are good at reading. Nothing makes me more mad than trying to find information about a framework/sdk/library to see if it will have any use for me in a 2 hour long video. Here is a common strategy: ...


1

I guess it depends on who owns the codec you are changing and the license that is associated with it. Also if you intend to sell or give away. Probably the best/safest way is to approach the codec owner - amybe they will even assess your hack with intent to absorb it into the codec itself. As with anything potentially coprighted, there are mine fields ...


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