BBC One HD

[fabje]

Hello,

I have a recording of BBC One HD.
When I view this recording the video is fine, but when I cut the .ts file in DGAVCIndex and after that convert the .h264 file to an .ts file using TSMuxer.
I load this .ts file in Staxrip but then I see a lot of glitches and I don't have a clue why.

Here are two snapshots.
Source @ VLC


Preview @ Staxrip


Here is a part of the .ts, I used H.264 TS Cutter 111 to create this file.

If you can't play the file use VLC.

[Shevach]

I experienced this sort of visual distortion on cut excerpts.
Two things can cause these distortions:
a) incorrect "cut-method"
b) bad error-handling mechanism in a decoder.

As to the item (a) the stream should be cut at random access points (usually signaled by IDR or recovery point SEI). Therefore any utility tailored to cut a stream should look for recovery (or random access) point and cut the stream at this point. Unfortunately some commercial streams have no random access points. In such case usually the stream is cut at I-picture and visual distortions are inevitable.

As to the item (b): if an excerpt is cut at a I-picture which is not a random access point then the following pictures might refer to non-existing references. In such case ErrorHandling mechanism of a decoder should minimize visual distortion.
There are strategies to minimize visual distrotions:
(i) if the decoder sees MB with reference indexes pointing on non-existing reference pictures then it simply changes the reference index to point on some existing reference picture. As a result visual distortions of the presented kind might appear especially if significant motion has take.
(ii) On the other hand the decoder can discard (not display) a picture where the number of illegal reference indexes exceed some pre-defined threshold.

To decide whether display or discard errorenuous picture a clever decoder should estimate blockiness level at the decoded picture and if the blockiness level significantly differs from those of the previous picture then it has to discard this picture.
It's better to observe jitter than mosaics distrotion.

On conclusion one can check whether BBC stream have random access points. If false then one can find "more clever" decoder.

[fabje]

On conclusion one can check whether BBC stream have random access points. If false then one can find "more clever" decoder.
Do you know a tool what I can use to check about the access points? Or other cut programs.

[Ghitulescu]

Smartcutter, reports are that it preserves even the subtitles (which is not a given for most if not all other cutters).

[J_Darnley]

Aren't those errors because DGAVCIndex does not support PAFF?

[Shevach]

Do you know a tool what I can use to check about the access points? Or other cut programs.

Vega H264 analyzer

[kieranrk]

Aren't those errors because DGAVCIndex does not support PAFF?

Yes that is true.

[fabje]

Aren't those errors because DGAVCIndex does not support PAFF?
Do you know a program that supports PAFF?

[J_Darnley]

DGDecNV, newer versions of libavcodec, other DirectShow decoders

[LoRd_MuldeR]

newer versions of libavcodec

=> FFmpegSource2 (http://code.google.com/p/ffmpegsource/)

[mitsubishi]

Hi, sorry for my curtness, I'm in a hurry. Currently to convert BBC HD streams I do the following:

-Cut with TsRemux, leaving 300+ frames at start.
-Open the new TS in Avisynth script with DSS2, using ffdshow with libavcodec selected (ie not MT)
-Add what I need to script, usually trimming off end frames (but not start frames).
-Write out a lossless file from script
-Encode using "--seek ???" and "--fps 25"

I've ending up doing this because I couldn't find anything else reliable and error free. DivX HD, ffmpeg-mt, DGAVCdec etc all had issues. Even this way I need to do a lossless run, since giving x264 the avs results in corruption, I think something to do with --rc-lookahead, whatever it is, it worsens at higher presets. x264's huffy decode in 64bit is not correct, but looks fine, 64bit also needs fps setting.

[nm]

I've ending up doing this because I couldn't find anything else reliable and error free. DivX HD, ffmpeg-mt, DGAVCdec etc all had issues. Even this way I need to do a lossless run, since giving x264 the avs results in corruption, I think something to do with --rc-lookahead, whatever it is, it worsens at higher presets.

Sounds like a DirectShow(Source) issue. Have you tried FFMS2 at all?

[mitsubishi]

Sounds like a DirectShow(Source) issue. Have you tried FFMS2 at all?

Yeah, I tried ffmpeg source, I cannot remember what issue I had, but there was something that made me dismiss it. It may have been a frame dropping or frame skipping issue. I shall recheck, but I had 2.15 then.