[Cin] Set stream sample aspect ratio in ffmpeg.C

[Terje J. Hanssen]

Den 05.01.2024 16:19, skrev Terje J. Hanssen:
>
>
> Den 05.01.2024 02:58, skrev Andrew Randrianasulu:
>> On Fri, Jan 5, 2024 at 3:59 AM Andrew Randrianasulu
>> <randrianasulu at gmail.com> wrote:
>>>
>>>
>>> пт, 5 янв. 2024 г., 02:59 Andrew Randrianasulu 
>>> <randrianasulu at gmail.com>:
>>>>
>>>>
>>>> пт, 5 янв. 2024 г., 02:53 Phyllis Smith <phylsmith2017 at gmail.com>:
>>>>> Bummer, although this does fix the 1 problem as discovered by 
>>>>> Terje, it breaks Bluray and DVD creation.  You can easily see this 
>>>>> without having a bluray writer simply with these steps:
>>>>> 1) load video with audio which in my case was 1440x1080 (from a 
>>>>> sony camera)
>>>>> 2) pulldown Settings/Format and switch to HDV 1080/25
>>>>> 3) pulldown File and select bd_render
>>>>>
>>>>> Error is:  FFMPEG::encode_activate: write header failed 
>>>>> /tmp/bd_20240104-164102/bd.m2ts
>>>>>    err: Invalid argument
>>>
>>> To be honest it errs out for me even without my patch?
>>>
>>> FFMPEG::encode_activate: write header failed 
>>> /data/data/com.termux/files/home/tmp/bd_20240105-035457/bd.m2ts
>>>    err: Math result not representable
>>>
>>> for 1440*1080 hdv sample without setting format first (it sets 
>>> itself on media autoload) and using default bd render params 
>>> (1440*1080, 25i)
>>>
>>>
>>
>> ah, it was due to using system (unpatched) ffmpeg!
>>
>> Try this series instead, it guards setting stream sample aspect ratio
>> only to muxers supporting it
>> (I grep in libavformat for sample_sapect)
>>
>> I tested avi, qt, y4m, matroska
>>
>>
>>>>> In DVD creation, it does create the DVD without erring out, but 
>>>>> the DVD will not even load on an LG DVD/Bluray device hooked up to 
>>>>> the TV.  It plays on the Samsung UHD but hangs on 1 part towards 
>>>>> the end.
>>>>
>>>>
>>>> So, I guess it should not be applied for at least m2ts and mpeg2 
>>>> containers ..... I'll try to limit it only to mov/mp4/mkv/webm .
>>>>>
>>>>> The patch probably has other unknown ramifications that I have not 
>>>>> found.  Neither HV or CV have an existing "ffmpeg.C" file in the 
>>>>> cinelerra subdirectory for comparison.
>>>>>
>>>>>
>>>>> On Sat, Dec 30, 2023 at 10:31 AM Andrew Randrianasulu 
>>>>> <randrianasulu at gmail.com> wrote:
>>>>>> Now it seems to display correct (16/9) DAR for sample encoded 
>>>>>> directly from hdv. (but for speed I tested vp8/webm, not av1/webm)
>>>>>>
>>>>>>
>
> I have not tested it and don't know how this works. But shouldn't it 
> in principle keep or preserve the HDV 1080i "anamorphic flag" so 
> players detect to stretch it horizontally to DAR 16:9?
> This also due to the fact that the HDV videopart should be possible to 
> copy directly to BD without rendering (or similar if downscaling to a 
> DV(D) anamorphic widescreen format).
>

This technical primer is one of the better I've seen about  "Aspect 
Ratio and Digital Video". And I noted especially the last section "Best 
practices when working with anamorphic video"
http://www.miraizon.com/support/info_aspectratio.html