gst-plugins-base: decodebin2: Don' t use the same element multiple times in the same chain

[Jan Schmidt]

Hi,

In the past, we've seen files that have at least 2 layers of id3, or
even id3 wrapped around avi and the streams contain id3. This commit
sounds like it will break those.

J.

On Sat, 2011-02-26 at 14:41 -0800, Sebastian Dröge wrote:
> Module: gst-plugins-base
> Branch: master
> Commit: 5058f792263e4214f4655c5ed5956ebfbeb17c99
> URL:    http://cgit.freedesktop.org/gstreamer/gst-plugins-base/commit/?id=5058f792263e4214f4655c5ed5956ebfbeb17c99
> 
> Author: Sebastian Dröge <sebastian.droege at collabora.co.uk>
> Date:   Sat Feb 26 23:39:03 2011 +0100
> 
> decodebin2: Don't use the same element multiple times in the same chain
> 
> This is going to lead to an infinite loop of this element and can easily
> happen with parsers that accept their own src caps on the sinkpad.
> 
> ---
> 
>  gst/playback/gstdecodebin2.c |   25 +++++++++++++++++++++++++
>  1 files changed, 25 insertions(+), 0 deletions(-)
> 
> diff --git a/gst/playback/gstdecodebin2.c b/gst/playback/gstdecodebin2.c
> index caa3c42..339ec91 100644
> --- a/gst/playback/gstdecodebin2.c
> +++ b/gst/playback/gstdecodebin2.c
> @@ -1667,6 +1667,8 @@ connect_pad (GstDecodeBin * dbin, GstElement * src, GstDecodePad * dpad,
>      GstElement *element;
>      GstPad *sinkpad;
>      gboolean subtitle;
> +    gboolean skip = FALSE;
> +    GList *l;
>  
>      /* Set dpad target to pad again, it might've been unset
>       * below but we came back here because something failed
> @@ -1678,6 +1680,29 @@ connect_pad (GstDecodeBin * dbin, GstElement * src, GstDecodePad * dpad,
>      /* Remove selected factory from the list. */
>      g_value_array_remove (factories, 0);
>  
> +    /* First check if this is a factory for which we have already
> +     * created an element in this chain. If we have, we skip this
> +     * factory because it will lead to an infinite loop. Examples
> +     * for this are parsers that accept their own src caps on the
> +     * sinkpad again.
> +     */
> +    CHAIN_MUTEX_LOCK (chain);
> +    for (l = chain->elements; l; l = l->next) {
> +      GstElement *otherelement = GST_ELEMENT_CAST (l->data);
> +
> +      if (gst_element_get_factory (otherelement) == factory) {
> +        skip = TRUE;
> +        continue;
> +      }
> +    }
> +    CHAIN_MUTEX_UNLOCK (chain);
> +    if (skip) {
> +      GST_DEBUG_OBJECT (dbin,
> +          "Skipping factory '%s' because it was already used in this chain",
> +          gst_plugin_feature_get_name (GST_PLUGIN_FEATURE_CAST (factory)));
> +      continue;
> +    }
> +
>      /* emit autoplug-select to see what we should do with it. */
>      g_signal_emit (G_OBJECT (dbin),
>          gst_decode_bin_signals[SIGNAL_AUTOPLUG_SELECT],
> 
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-- 
Jan Schmidt <thaytan at noraisin.net>