[FFmpeg-devel] [PATCH] fftools/ffmpeg: fix -t inaccurate recording time

[Gyan Doshi]

On 2021-07-09 11:03, Shiwang.Xie wrote:
> Pings.

Will test.

>
> On Sat, 5 Jun 2021, Shiwang.Xie wrote:
>
>> Ping.
>>
>> Thanks,
>> Shiwang.Xie
>>
>> On Sat, 29 May 2021, Shiwang.Xie wrote:
>>
>>> Hi, any updates for this?
>>>
>>> Thanks,
>>> Shiwang.Xie
>>>
>>> On Wed, 19 May 2021, Shiwang.Xie wrote:
>>>
>>>> Hi, is there objection?
>>>>
>>>> Thanks,
>>>> Shiwang.Xie
>>>>
>>>> On Sat, 15 May 2021, Shiwang.Xie wrote:
>>>>
>>>>> if input start time is not 0 -t is inaccurate doing stream copy,
>>>>> will record extra duration according to input start time.
>>>>> it should base on following cases:
>>>>>
>>>>> input video start time from 60s, duration is 300s,
>>>>> 1. stream copy:
>>>>>       ffmpeg -ss 40 -t 60 -i in.mp4 -c copy -y out.mp4
>>>>>   open_input_file() will seek to 100 and set ts_offset to -100,
>>>>>   process_input() will offset pkt->pts with ts_offset to make it 0,
>>>>>   so when do_streamcopy() with -t, exits when ist->pts >= 
>>>>> recording_time.
>>>>>
>>>>> 2. stream copy with -copyts:
>>>>>       ffmpeg -ss 40 -t 60 -copyts -i in.mp4 -c copy -y out.mp4
>>>>>   open_input_file() will seek to 100 and set ts_offset to 0,
>>>>>   process_input() will keep raw pkt->pts as ts_offset is 0,
>>>>>   so when do_streamcopy() with -t, exits when
>>>>>   ist->pts >= (recording_time+f->start_time+f->ctx->start_time).
>>>>>
>>>>> 3. stream copy with -copyts -start_at_zero:
>>>>>       ffmpeg -ss 40 -t 60 -copyts -start_at_zero -i in.mp4 -c copy 
>>>>> -y out.mp4
>>>>>   open_input_file() will seek to 120 and set ts_offset to -60 as 
>>>>> start_to_zero option,
>>>>>   process_input() will offset pkt->pts with input file start time,
>>>>>   so when do_streamcopy() with -t, exits when ist->pts >= 
>>>>> (recording_time+f->start_time).
>>>>>
>>>>> 0      60     40      60                     360
>>>>> |_______|_____|_______|_______________________|
>>>>>      start   -ss     -t
>>>>>
>>>>> This fixes ticket #9141.
>>>>>
>>>>> Signed-off-by: Shiwang.Xie <shiwang.xie666 at outlook.com>
>>>>> ---
>>>>> fftools/ffmpeg.c | 8 +++++---
>>>>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
>>>>> index b3658d8f65..309d9dfa6e 100644
>>>>> --- a/fftools/ffmpeg.c
>>>>> +++ b/fftools/ffmpeg.c
>>>>> @@ -2082,9 +2082,11 @@ static void do_streamcopy(InputStream *ist, 
>>>>> OutputStream *ost, const AVPacket *p
>>>>>     }
>>>>>
>>>>>     if (f->recording_time != INT64_MAX) {
>>>>> -        start_time = f->ctx->start_time;
>>>>> -        if (f->start_time != AV_NOPTS_VALUE && copy_ts)
>>>>> -            start_time += f->start_time;
>>>>> +        start_time = 0;
>>>>> +        if (copy_ts) {
>>>>> +            start_time += f->start_time != AV_NOPTS_VALUE ? 
>>>>> f->start_time : 0;
>>>>> +            start_time += start_at_zero ? 0 : f->ctx->start_time;
>>>>> +        }
>>>>>         if (ist->pts >= f->recording_time + start_time) {
>>>>>             close_output_stream(ost);
>>>>>             return;
>>>>> -- 
>>>>> 2.18.5
>>>>>
>>>>>
>>>>
>>>
>>
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