Problem with ffmpeg or the source?

[Andy Bircumshaw]

On 17/12/2010, at 12:20pm, Shevek wrote:
> ...
> Remux HD using latest ffmpeg:
> http://paje.ro/wp-content/uploads/2010/12/hd_r26041.png

I've definitely seen this - and other glitches - on a number of occasions.

Grepping my .maildir I find 3 instances of the "brainfart" message, all on different days.:

7 December 2010 - Garrows Law Series 2 - Episode 4 b00wljbb
8 December 2010 - The Trip - 6. The Angel at Hetton b00wmxnm
9 December 2010 - Natural World - 2010-2011 7. Panda Makers b00wmvl6

My email's trash folder gets cleared after 2 weeks, so these will be all the occasions on which this has occurred during this period.

However, I haven't watched any of these programmes yet. I have seen a pink bar very similar to that in your screenshot on shows recorded months ago.

One of the other glitches I have experienced has been a thin scatter of pink (just the same shade as in your screengrab) or white pixels for just a fraction of a second. I would guess maybe 20 single pixel "stars" spread out widely and fairly evenly over the screen. Another, on other occasions, is a stutter in the sound lasting maybe ½ - 1 second. None of these I have noticed this month, although I have watched very little the last 3 weeks.

Installation dates of ffmpeg versions:

$ genlop ffmpeg | tail -n 4
     Thu May 27 18:21:20 2010 >>> media-video/ffmpeg-0.5_p20373
     Fri Oct  8 15:05:31 2010 >>> media-video/ffmpeg-0.6
     Tue Dec 14 00:31:18 2010 >>> media-video/ffmpeg-0.6_p25767
$ 

I have seen another error in the ffmpeg logs. I can't remember the text of it, but I'm sure I've seen the same message on more than one occasion, and I assumed it might be responsible for these problems. As I recall the error is in mid-stream, not at the beginning of the remux (as is the "brainfart" message you have observed).

The problem is that I don't watch a programme until days after I downloaded it, so I don't remember about the error message. If I see these glitches during viewing I may very well no longer have the logfiles. Although the error message is mid-stream, there is no timestamp for it in the log, so one can't easily skip through the download to see if the error message is directly related to an anomaly at the same point in the stream.

I thought about discussing this on the ffmpeg mailing list, to see if a timestamp could be added for mid-stream error messages. I guess I could even look at the source, next time I notice one. This isn't very pressing to me. It would be *nice* if the recordings were perfect, but I can live with it. Actually, what bugs me more is to learn that this is a problem with our software, not the BBC being lame; now I want to fix the problem.

I'm really tired right now & can't process the implications of what you've observed, vs. my different version of ffmpeg. Perhaps my revision numbers and the dates of the errors I have seen will help you with regression testing. Clearly this only affects some shows, as I have downloaded many more than these 3 during this period.

I guess I associate "cropping" somehow with aspect ratio, because the message's reference to that reminded me of this thread on the BBC iPlayer forums:
http://www.bbc.co.uk/dna/mbiplayer/NF13735683?thread=7927082
I can't help but wonder if this problem might be influenced by the Beeb posting the shows in the wrong format, or something. Or maybe I'm just trying to blame them because I'm mad about the other shows I've missed recently because they've been unavailable.

aB.