[FFmpeg-devel] [PATCH]select attribute of tee pseudo demuxer may contain multiple stream specifiers

[Bodecs Bela]

2015.10.04. 20:06 keltezéssel, Nicolas George írta:
> Le tridi 13 vendémiaire, an CCXXIV, Bodecs Bela a écrit :
>> git format-patch -n -o /tmp/ --attach  origin
> Thanks. Any particular reason to use --attach? It is not a big issue, just a
> matter of curiosity.
I thought I should use it this way to be able to send the created patch 
file later with any mailer.

>
>>>> @@ -172,15 +175,26 @@ static int open_slave(AVFormatContext *avf, char *slave, TeeSlave *tee_slave)
>>>>       for (i = 0; i < avf->nb_streams; i++) {
>>>>           st = avf->streams[i];
>>>>           if (select) {
>>>> -            ret = avformat_match_stream_specifier(avf, avf->streams[i], select);
>>>> -            if (ret < 0) {
>>>> -                av_log(avf, AV_LOG_ERROR,
>>>> -                       "Invalid stream specifier '%s' for output '%s'\n",
>>>> -                       select, slave);
>>>> -                goto end;
>>>> -            }
>>>> +            fullret = 0;
>>>> +            first_subselect = select;
>>>> +            next_subselect = NULL;
>>>> +            while (subselect = av_strtok(first_subselect, slave_select_sep, &next_subselect)) {
>>>> +                first_subselect = NULL;
>> You would be right unless I used
>>
>> first_subselect = NULL;
>>
>> right after the while statement, so the next round av_strtok will go
>> further, because the first parameter will be null, not the same string and
>> next_subselect will point the next start.
>> Yes it is destructive, but we never use this string (select) again in this
>> function.
> I suspect we are talking at cross-purpose here. The "first_subselect = NULL"
> you are talking about is in the while loop for av_strtok(), it is indeed the
> normal way of using av_strtok().
>
> But I was talking about the surrounding for loop that goes over all the
> streams. I left the code quoted above for reference. For i=0, the code is
> valid, but as soon as i>=1, "first_subselect = select" will use a truncated
> string
>
>> I swear, I have really tested it, I use it on my own  in my production
>> environment.
> I do not believe that you neglected to test it (nor that you are lying, of
> course!), I am just really surprised. Just to be sure, I just tested, adding
> a debug log just after "first_subselect = select", with the following
> command-line:
>
> ./ffmpeg_g -lavfi 'testsrc=r=5;testsrc=r=7;testsrc=r=11' \
>    -c:v rawvideo -f tee '[f=framecrc:select=0,1]-'
>
> I get the following output:
>
> select = '0,1'
> select = '0'
>      Last message repeated 1 times
> [tee @ 0x36143e0] Input stream #1 is not mapped to any slave.
> [tee @ 0x36143e0] Input stream #2 is not mapped to any slave.
>
> The second "select =" line shows that it is working with a truncated line,
> and stream #1 should be mapped. Indeed, if I swap the specifiers: "1,0", it
> maps #0 and #1: #0 is matched first while the string is still intact, #1 is
> matched by the truncated string.
>
> Regards,
>
>

you are right. It is my mistake that I did not test it thoughtfully. It 
was bad luck why I did not receive error still now.
I will correct the patch  as soon as possible and send it again. I think 
I will use the av_strdup() to correct it. (and av_free, of course)

thank you,

Bela Bodecs

>
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