Frame accurate cutting on m2ts files?

[stryker412]

I was wondering if there was a free program available that allows for frame accurate editing with (video previews) on m2ts files? Also is there something available for mkv files too?

[Dragonfiii]

I tried searching for tool to cut .m2ts accuractly, but I was not able to find a freeware tool that could do it properly.
There is a software called Smart Cutter which does it spot on accurat, but it is only able to do this because it encodes the begining and the end of the cut you end up with.

I don't think there are any tools that can do it differently and still be accurate.

[edDV]

Transport stream containers (ts, m2t, m2ts, MTS) are intended for distribution through harsh environments, still most have short 12-15 frame GOPs. MKV is mostly used for long GOP low bit rate internet downloads. Neither is intended for editing but for distribution. Within the transport stream various error correction schemes keep audio and video in sync.

In either the video encoding doesn't exist as frames but as a full I frame followed by change data to make up the rest of the GOP. Audio exists as a bit stream at a constant sample rate. Such A/V streams can be edited on the I frame and audio will usually keep in sync with cut video.

If you demux the video and audio streams from the transport stream container, each exists as independent streams with no means of synchronization. They just free run.

Usually audio decodes faster than video. This can result in an offset of video vs audio time displacement. If the streams play at slightly different speeds, then the time displacement increases or in some cases decreases.

If you want to cut inside the GOP, the brute force solution is to manually adjust audio speed to match video or to cut audio chunks or add dummy chunks to the audio track to match lip sync at critical points in the program.

[Dragonfiii]

hey edDV great information, thanks