[FFmpeg-devel] 0001-fix-segment-fault-in-function-decode

[FFmpeg-devel] 0001-fix-segment-fault-in-function-decode

[陈督]

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 /*When it is not a planar arrangement, data[1] is empty,

    and all the data is interleaved in data[0].

    This can result in a segmentation fault when accessing data[ch] .*/

    //So I delete the code below:

    for (i = 0; i < frame->nb_samples; i++)

        for (ch = 0; ch < dec_ctx->ch_layout.nb_channels; ch++)

            fwrite(frame->data[ch] + data_size*i, 1, data_size, outfile);




    //And I write this instead

        // L R data order

    if (av_sample_fmt_is_planar(dec_ctx->sample_fmt))

    {

        // planar：LLL...RRR... in different data[ch]

        for (ch = 0; ch < dec_ctx->ch_layout.nb_channels; ch++)

        {

            fwrite(frame->data[ch], 1, frame->linesize[0], outfile); // only linesize[0] has data.

        }

    }

    else

    {

        // not planar：LRLR...all in data[0]

        fwrite(frame->data[0], 1, frame->linesize[0], outfile);

    }



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Re: [FFmpeg-devel] 0001-fix-segment-fault-in-function-decode

[Stefano Sabatini]

On date Saturday 2024-01-13 05:57:18 +0800, 陈督 wrote:
> 
> 
>  /*When it is not a planar arrangement, data[1] is empty,
> 
>     and all the data is interleaved in data[0].
> 
>     This can result in a segmentation fault when accessing data[ch] .*/
> 
>     //So I delete the code below:
> 
>     for (i = 0; i < frame->nb_samples; i++)
> 
>         for (ch = 0; ch < dec_ctx->ch_layout.nb_channels; ch++)
> 
>             fwrite(frame->data[ch] + data_size*i, 1, data_size, outfile);
> 
> 
> 
> 
>     //And I write this instead
> 
>         // L R data order
> 
>     if (av_sample_fmt_is_planar(dec_ctx->sample_fmt))
> 
>     {
> 
>         // planar：LLL...RRR... in different data[ch]
> 

>         for (ch = 0; ch < dec_ctx->ch_layout.nb_channels; ch++)
> 
>         {
> 
>             fwrite(frame->data[ch], 1, frame->linesize[0], outfile); // only linesize[0] has data.
> 

The problem with this approach is that this is generating output in a
format which cannot be played by ffplay, which is assuming packed
(i.e. non planar) format. So it is expecting the output file to be
written as:
LRLRLR...

rather than as:
LLLLLL....RRRRR

also because ffplay does not know the linesize.

...

But I see the example code should be fixed, it was designed with the
assumption that the input sample format was always packed, which is
not the case anymore.

[...]
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