In the video for Web: quality and compression

Very often we hear about the importance of the famous bitrate, but ... what is the bitrate? The bitrate determines the amount of bits of information that contain our video production in a second. And you might be wondering ... what does that imply? It implies that the higher the bitrate, the more the resulting file will have, but at the same time, the greater its size. So what bitrate we choose? They will choose the maximum bitrate possible, always bearing in mind the limitations of the target media where it is to play our production. For example, knowing that the capacity of a standard DVD (DVD-5) is 4.7 GB, if you want to store a movie of, say, about 90 minutes, we can never overcome a bitrate of 8.7 Mbps, since we generate a file size greater than one's own capacity optical disc. Generally, they usually choose bitrates of up to 5 Mbps for DVD productions. And going to what concerns us here, what is the appropriate bitrate for a video site? The bitrate of a video for the web will be determined: first, the order for production, ie the number of pixels in each frame of video. A higher resolution will require more bits of information for each image, every second, also influence the transmission bit rate Internet provider of the beholder.

Knowing that are currently offering data transmission speeds of 6 Mbps, it would make sense to create a file for viewing online, with a bitrate of 8 Mbps, and the actual capacity of the server that hosts it. For example, YouTube, the referring site to share video, flash converter has its own in place that greatly limits the bitrate automatically for each file that is uploaded to the server.

Another issue: is it really HD video on a website? Do not confuse the term "high definition? (HD) with the "High Quality? (HQ) that begins to circulate through the network. The sine qua non for a video posted on a website can be viewed in HD, are as follows: It is necessary that the video file has been created at a resolution of 1920x1080 pixel frame is also necessary that the viewer has a monitor capable of reproducing a resolution of 1920x1080 pixels, in addition, the viewer must have a computer able to process the volume of data from a high-definition video without dropped frames, and also recommended bitrates of between 7 and 10 Mbps for encoding videos in HD, figures difficult to achieve with current connections Internet.Si basic premises of the four fails, we can not say we're seeing high-definition video, although a high-quality video, which is a more generic term. and what are they, and what role video codecs? In Europe, every second of film contains 25 frames, and if it comes to standard definition, every frame, every second of film contains more than 400,000 pixels.

By four issues, we realize that without compression, few computers would be able to process video files. The codecs (coder-decoder) define standards or specifications on how to proceed when compressing digital data, depending on the destination format or media of each production. All digital video created for dissemination has been encoded using a particular codec compression. Depending on the scope of an audiovisual media, the producer will use a video codec or another. The videos for the web usually are encoded in Flash Video format (flv extension) or H.264 format. Current versions of Flash used On2VP6 codec to compress video, and H.264 format is based on the MPEG-4. In short, how to adjust the balance between quality and compression to achieve the perfect balance? That's the million dollar question. It is very difficult to determine, by way of prescription, all commands must meet web video, which will guarantee the highest quality possible, since each project has a specific technical requirements. To summarize, I commented that: Atractium work since the beginning of the chain of production (shooting), the highest possible resolution (HDV).

Thus, whenever we have time to reduce frame sizes, if deemed appropriate. Also we consider who the potential viewer of the video of each of our clients, which are expected to be Internet access and transmission speeds, and of course, what is the capacity and speed of each video server that will host.