MPEG

How do you create MPEG data?

Q)

Please tell me about creating MPEG data.

A)

Commercially available MPEG encoder boards have become increasingly inexpensive in recent years, but the image quality produced by most of them seems to be less than flattering.
The encoded quality depends on the internal processing algorithm of the actual encoder LSI, but most importantly depends on the quality of the front-end circuit that A/D converts the input analog video signal.
The more expensive the product, the better it is because it takes into consideration the connection to professional video equipment, and by checking the time code from the external device, it is possible to encode and output only a specified time range. There are also some products.
Although it is possible to obtain encoded data using inexpensive products, it is true that if the image size is large, the frame rate will be limited to 15fps, and it will require considerable effort as it cannot be linked with other devices. .
It is true that cheaper products require more labor costs.
If you want to do the work reliably, you can also request the studio that actually undertakes the authoring work.
To actually do the authoring, you need to consider what kind of final form you want (image size, video CD, or call it from a program as an MPEG stream), so please contact us once. Please consult us.

There is a delay in audio playback when playing MPEG.

Q)

When I play back interleaved MPEG audio/MPEG video data using VCDBUILD, the video starts playing immediately, but the audio data starts playing with a delay.

A)

This is a known bug in VCDBUILD.
In the MPEG-1 system stream, in order to facilitate audio/video synchronization, the video stream, which takes time to decode when performing interleaving processing, is placed at the rear by inserting dummy data, and a margin is provided. Synchronization processing is performed based on the timestamp recorded in the audio/video stream.
However, some encoders handle a group of pictures (GOP), which in MPEG is a small movie, as a group of images. (This is because compression is applied.) is a closed GOP (Closed GOP: A GOP with no dependencies between the preceding and succeeding GOPs. MPEG is generated from a close relationship with the preceding and succeeding data, so there are , in other words, you can generate your own image from the data in front of you.Closed GOP is a data style that does not have such dependency between the front and back.)The standard is to output a stream like this. This is due to a problem with ``coherence'' when crossing GOPs in VCDBUILD.
The current solution is to encode the video stream using non-closed GOP.
In the case of a stream that has already been encoded, there is a way to forcibly lower the GOP flag of the GOP layer, but this is a very tedious process and is not recommended.