Re: When Streaming - 'dd' Value too large for defined data type

[Pádraig Brady]

On 06/12/2014 09:31 AM, address@hidden wrote:
> I have a script which uses 'dd' (instead of 'cat') for capturing a timed DVB 
> stream or feed for 30, 60, 90, ... minutes.  (From memory, I stopped using 
> 'cat' a long time ago either because 'cat' had problems with TV channels 
> containing static or due to large file size.)
> 
> A sporadic error received when using 'dd' is the following:
> 
> --- Snip ---
> /mnt/archives1/tv/20140611-1700-ch9.1-60min.mpg                               
>                                                               
> dd: error reading '/dev/dvb/adapter0/dvr0': Value too large for defined data 
> type                                                           
> 73145+0 records in                                                            
>                                                               
> 73145+0 records out                                                           
>                                                               
> 37450240 bytes (37 MB) copied, 38.2406 s, 979 kB/s                            
>                                                               
> dd: warning: invalid file offset after failed read
> --- Snip ---
> 
> My guess is, since dd doesn't know the exact initial size or the proper 
> number 
> of interval bytes, dd spawns this error.  Or, there maybe static within the 
> signal or overload.  Although my rational doesn't seem to match the given 
> error, sometimes errors might be just generic in a sense.  (ie. 'dd' was 
> likely 
> engineered for file copying, and copying a live stream was later.)
> 
> My second guess, there's likely no way to avert the error and is likely a 
> harmless error.
> 
> Channel 9.1 is PBS at my location over DVB TV, a large file at times:
> VIDEO:  MPEG2  1280x720  (aspect 3)  59.940 fps  24000.0 kbps (3000.0 kbyte/s)
> AUDIO: 48000 Hz, 2 ch, ac3be, 384.0 kbit/25.00% (ratio: 48000->192000)
> 
> Bottom line, the recorded video file (stream) looks just fine and I don't 
> think 
> I've ever seen any anomalies.  If any video/audio problems created by this 
> error, I've never see a player or editor complain, or the editor 
> automatically 
> fixes the file.
> 

It seems dd is only reporting the EOVERFLOW from the read() syscall.
That error seems specific to the kernel DVB drivers:
https://tvheadend.org/boards/5/topics/8378?r=8414

cheers,
Pádraig.