[FFmpeg-devel] (No Subject)

[Ramiro Polla]

Hi,

On Thu, Oct 17, 2024 at 8:38 AM Cynthia via ffmpeg-devel
<ffmpeg-devel at ffmpeg.org> wrote:
> From d7863bab8e1028b6cfb3ce848e216e86ff00eca0 Mon Sep 17 00:00:00 2001
> From: cynthia2006 <cynthia2048 at proton.me>
> Date: Tue, 28 May 2024 22:03:50 +0530
> Subject: [PATCH] lavc/mjpegdec: add option for ignorning malformed APPx
>  segments
> X-Unsent: 1
> To: ffmpeg-devel at ffmpeg.org
>
> A few cameras, namely Logitech C270 or similar produce MJPEG frames containing
> malformed APP0 chunks, and as a result of which, FFmpeg spams stdout with
>
> "[mjpeg @ 0xcoffeebabe] unable to decode APP fields: Invalid data found when processing input"
>
> The issue is explained in full-detail here: https://stackoverflow.com/q/55439184.
> TL;DR The second APP0 chunk is the culprit here.
>
> Issue is mitigated if those segments are ignored. This patch adds a MJPEG decoder private
> option `-allow_malformed_app` which if enabled, ignores those malformed APP0 segments.

I took a different approach where, instead of adding a new option, I
just silently ignore APPx stubs. I'll send my patches in a while.

> Signed-off-by: cynthia2006 <cynthia2048 at proton.me>
> ---
>  libavcodec/mjpegdec.c | 5 +++++
>  libavcodec/mjpegdec.h | 1 +
>  2 files changed, 6 insertions(+)
>
> diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
> index 1481a7f285..b1e26044c0 100644
> --- a/libavcodec/mjpegdec.c
> +++ b/libavcodec/mjpegdec.c
> @@ -1863,6 +1863,9 @@ static int mjpeg_decode_app(MJpegDecodeContext *s)
>              av_log(s->avctx, AV_LOG_WARNING, "skipping APPx (len=%"PRId32") for bayer-encoded image\n", len);
>              skip_bits(&s->gb, len);
>              return 0;
> +        } else if (s->allow_malformed_app) {
> +            skip_bits(&s->gb, len);

len is in bytes, so this call to skip_bits() is not correct. I know
it's the same as in the existing code above, but that should be fixed
as well.

> +            return 0;
>          } else
>              return AVERROR_INVALIDDATA;
>      }