[vlc] Re: Debug error messages

[Måns Rullgård]

"Paul Rae" <PRae at aminocom.com> writes:

> I'm trying to debug a couple of streams a customer has sent us and
> was wondering if you can cofirm what some of your debug messages
> mean:

Are these transport streams?

> Error 1:
> main warning: backward_pts != current_pts (-40000)
> main debug: stream periodicity changed from P[5] to P[3]
> main warning: output date isn't PTS date, requesting resampling (62870)
> main warning: buffer is 60704 late, triggering upsampling
> main warning: PTS is out of range (-7266), dropping buffer
> main warning: PTS is out of range (-30044), dropping buffer
> main warning: output date isn't PTS date, requesting resampling (42453)
> main warning: buffer is 60685 late, triggering upsampling
>
> Now I'm assuming this refering to the PTS time-stamps jumping
> backwards in time occasionally. Likely causes of this being packets
> delivered out of order, or possibly dropping some packets

Those errors usually indicate bad PCR values in the TS.

> Error 2:
> main warning: late picture skipped (173512)
> main warning: late picture skipped (133512)
> main warning: late picture skipped (92089)
> main warning: late picture skipped (52089)
>
> Again im assuming this is indicating late delivery of packets on the
> network

Bad PCR again.

> Error 3:
> ts warning: discontinuity received 0xb instead of 0x2
> ts warning: discontinuity received 0xf instead of 0x2
> ts warning: discontinuity received 0xd instead of 0x7

Lost packets.

> main warning: computed PTS is out of range (8157771), clearing out
> main warning: timing screwed, stopping resampling
>
> Can you confirm what the error indicates.

PCR, once more.

> Error 4:
> main warning: PTS is out of range (8222423), dropping buffer
> main warning: output PTS is out of range (8197813), clearing out
> main warning: PTS is out of range (7919589), dropping buffer
> main warning: PTS is out of range (7895589), dropping buffer
> main warning: PTS is out of range (7871589), dropping buffer
>
> Again im assuming this is indicating late delivery of packets on the
> network which is causing PTS to be out of sync

And PCR yet another time.

> Error 5:
> main warning: dts != current_pts (-243823)
>
> Can you confirm what the error indicates.

Still PCR.

> Error 6:
> main debug: audio output is starving (46998), playing silence
>
> Assuming that audio delivery is late and are playing silence to fill gap.

You guessed it, PCR.

> Error 7:
> main warning: dts != current_pts (40234)
> main warning: timing screwed, stopping resampling
> main warning: buffer is 84465 late, triggering upsampling
> main warning: dts != current_pts (30955)
> main warning: dts != current_pts (27078)
> main warning: audio drift is too big (128383), dropping buffer
> main warning: dts != current_pts (19911)
> main warning: audio drift is too big (120327), dropping buffer
>
> Again audio buffer underflowing?

Do I need to repeat?  PCR.

> Error 8:
> main debug: stream periodicity changed from B[1] to B[2]
> main debug: stream periodicity changed from P[5] to P[3]
> main debug: stream periodicity changed from P[6] to P[3]
> main debug: stream periodicity changed from P[3] to P[4]
> main debug: stream periodicity changed from P[4] to P[3]
> main debug: stream periodicity changed from P[3] to P[4]
>
> Can you confirm what this error indicates.

Not an error.

The exact *meaning* of those error remains a mystery.  I have been
asking occasionally for a couple of years, and have yet to receive any
answer.

-- 
Måns Rullgård
mru at inprovide.com

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