MPEG

How to create MPEG data?

Q)

Please tell me about the creation of MPEG data.

A)

Although the number of commercially available MPEG encoder boards has increased in recent years, the image quality produced by most products does not seem to be flattering.
The quality to be encoded depends on the internal processing algorithm of the actual encoder LSI, but most 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 is considered to be connected to a professional video device, and by looking at the time code from an external device, it is possible to encode and output only the specified time range. There are also various products.
It is possible to obtain encoded data using an inexpensive product, but it is certain that it will take a lot of time and effort because the frame rate is limited to 15 fps and it can not be linked with other devices if the image size is large. ..
It is a fact that cheaper ones require labor costs.
If you want to be sure of the work, you can also ask the studio that actually undertakes the authoring.
In order to actually author, it is necessary to consider what kind of final form is required (image size, video CD, whether to call from the program as an MPEG stream), so please contact us once. Please contact us.

Audio playback is delayed due to MPEG playback.

Q)

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

A)

This is a known bug that has been identified in VCDBUILD.
In the MPEG-1 system stream, the video stream, which takes time to decode when performing interleaving processing for the purpose of facilitating audio / video synchronization, is placed backward by inserting dummy data to provide a margin. Performs synchronization processing based on the time stamp recorded in the audio / video stream.
However, some encoders treat GOP (Group Of Picture: image set, and MPEG treats a small movie as a set of separated images) as a group, because MPEG treats the images before and after. Closed GOP (closed GOP: GOP with no dependency between previous and next GOPs, MPEG is generated from the close relationship with the previous and next data, so it is not in my group In other words, you can generate your own image from the data in front of you. Closed GOP is such a data style that does not depend on before and after.) It is standard to output a stream that says. There is something that is wrong with the "successful" alignment when straddling the GOP in VCD BUILD.
The current countermeasure is to encode the video stream with non-closed GOP.
For streams that have already been encoded, there is a way to forcibly lower the GOP flag on the GOP layer, but this is a very tedious process and is not recommended.