[FFmpeg-devel] Suggested Patch for timecode timebase calculation in mov.c

jon jon at tweaksoftware.com
Fri Jan 23 15:44:56 CET 2015


Hi Michael,

That is great!

I see what you are referring to in mov_read_timecode_track(). However 
the text of that comment seems contradictory to me based on what I have 
read in the QuickTime reference I sited about the tmcd counter flag.

It seemed like prior to the patch I submitted mov_parse_stsd_data() was 
collecting the st->codec->time_base as if the counter flag was unset.

That comment text comes from commit:

35da85562d2f731855b28d4ab3b9b0679730ebf7

Perhaps Clément Bœsch has a better understanding of the difference 
between timecode values when the counter flag is set and when it is not. 
My work was based on deciphering the samples I had at my disposal in 
conjunction with my interpretation of the reference pdf.

Thanks,
Jon

On 1/23/15 5:12 AM, Michael Niedermayer wrote:
> On Fri, Jan 23, 2015 at 04:26:59AM +0100, Michael Niedermayer wrote:
>> On Thu, Jan 22, 2015 at 09:09:53AM -0800, jon wrote:
>>> I never heard back about this and I think I have a new better
>>
>> are you subscribed to ffmpeg-devel ?
>>
>>
>>> solution now. I don't think the current mov.c timecode processing is
>>> handling the case where the timecode is in counter mode. Please read
>>> the following page 190 from:
>>>
>>> https://developer.apple.com/library/mac/documentation/QuickTime/QTFF/qtff.pdf
>>>
>>> Specifically:
>>>
>>> "Number of frames
>>> An 8-bit integer that contains the number of frames per second for
>>> the timecode format. If the time is a counter, this is the number of
>>> frames for each counter tick."
>>>
>>> I have sample media in counter mode if it helps. I tried to send
>>> that before as well, but I think it was too large. Please let me
>>> know how else I can help with this enhancement. Feel free to send
>>> clarification questions to me.
>>
>> yes, please provide a sample
>> you can upload it via ftp see http://ffmpeg.org/bugreports.html
>> any url that allows downloading from with wget works too
>
> thanks for the sample
> seems to fix/improve it
>
> patch applied
>
> ive also spotted a text in mov_read_timecode_track() about the counter
> flag, this probably should be updated somehow
>
> [...]
>
>
>
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