[FFmpeg-user] I found the bugs

[Mark Filipak]

On 17/06/2024 17.18, Paul B Mahol wrote:
> On Mon, Jun 17, 2024 at 8:29 PM Mark Filipak <markfilipak.imdb at gmail.com>
> wrote:
> 
>> On 17/06/2024 13.50, Paul B Mahol wrote:
>>> On Mon, Jun 17, 2024 at 5:35 PM Mark Filipak <markfilipak.imdb at gmail.com
>>>
>>> wrote:
>>>
>>>> On 17/06/2024 03.16, Paul B Mahol wrote:
>>>>> On Mon, Jun 17, 2024 at 3:16 AM Mark Filipak <
>> markfilipak.imdb at gmail.com
>>>>>
>>>>> wrote:
>>>>>
>>>>>> To expand on my idea:
>>>>>>
>>>>>> The video is this:
>>>>>> I P B B P B B P B B I P B B..
>>>>>> I want to change it to this:
>>>>>> I B B P B B P B B P I B B P..
>>>>>>
>>>>>
>>>>> If this is what I think it is, your are wasting your time.
>>>>
>>>> It is possible. But can FFmpeg do it? You see, Paul, I read in several
>>>> places from seemingly
>>>> authoritative people that professional videos are PTS-ordered. I've
>> since
>>>> discovered that
>>>> professional videos are almost always DTS-ordered -- I now have a packet
>>>> browser and have seen it to
>>>> be true. However, I have seen professional videos that are PTS-ordered
>> but
>>>> I didn't think too much
>>>> about it at the time.
>>>
>>> PTS order is order once frames are decoded and going to be presented to
>>> user, thats why it is called presentation timestamps.
>>
>> Yes of course.
>>
>>>> My idea is to take the 4-second video -- DTS-ordered -- that I sent to
>>>> trac, change it to
>>>> PTS-ordered, and see if '-vf showinfo' and '-f show_frames' respond
>>>> correctly. It's a long shot, but
>>>> it might show something useful -- what if PTS-order made showinfo
>>>> show_frames and framecrc all
>>>> agree? Wouldn't that be something interesting?
>>>
>>> If decoder follows specifications for decoding bitstreams correctly than
>>> changing order of raw encoded frames as stored in bitstream will almost
>>> every-time cause broken decoding.
>>>
>>>>> Its nonsense to change order of encoded frames, no manipulation of
>> clock
>>>>> can fix that.
>>>>
>>>> No, no. Manipulation of PCR. Fix up the PCRs so that the result is truly
>>>> PTS-ordered.
>>>
>>> If this is at format container layer, I dunno how would that work even if
>>> its is possible to be useful.
>>
>> The container would contain a PES packet stream with PCRs like any other
>> PES packet stream. It would
>> work like any PTS-ordered stream does. You know, there _are_ PTS-ordered
>> streams. And you know, MPEG
>> is silent on the matter of what physical order frames are in the stream,
>> only that they must be
>> given to the decoder in DTS-order.
>>
>> Look, I agree that it would be nonsense. I want to turn the DTS-ordered
>> stream into a PTS-ordered
>> stream merely as a test: '-f show_frames' appears to be getting DTSes and
>> PTSes mixed up, then
>> applying a fix that results in completely new DTSes. If it treats the
>> PTS-ordered stream
>> differently, that will say a lot. What is says depends on what it does.
>> Capiche?
>>
>> I thought I could do it by demuxing, then moving them like you can move
>> frames in a filter_complex,
>> and then remuxing, but I don't know how to do that to PES packets (instead
>> of decoded pictures) and
>> I don't know how to rewrite PCRs.
>>
> 
> But aren't you working with HEVC and not MPEG video?

I'm working with AVC-M2TS, then transcoding-remuxing to HEVC-MP4.