diff mbox series

media: uvcvideo: Don't expose unsupported formats to userspace

Message ID 20230420100750.10463-1-laurent.pinchart@ideasonboard.com
State Superseded
Headers show
Series media: uvcvideo: Don't expose unsupported formats to userspace | expand

Commit Message

Laurent Pinchart April 20, 2023, 10:07 a.m. UTC
When the uvcvideo driver encounters a format descriptor with an unknown
format GUID, it creates a corresponding struct uvc_format instance with
the fcc field set to 0. Since commit 50459f103edf ("media: uvcvideo:
Remove format descriptions"), the driver relies on the V4L2 core to
provide the format description string, which the V4L2 core can't do
without a valid 4CC. This triggers a WARN_ON.

As a format with a zero 4CC can't be selected, it is unusable for
applications. Ignore the format completely without creating a uvc_format
instance, which fixes the warning.

Fixes: 50459f103edf ("media: uvcvideo: Remove format descriptions")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

Comments

Ricardo Ribalda May 1, 2023, 11:44 a.m. UTC | #1
Hi Laurent

I agree with the intent of the patch but am not sure that this will work.

Regards!

On Thu, 20 Apr 2023 at 12:07, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> When the uvcvideo driver encounters a format descriptor with an unknown
> format GUID, it creates a corresponding struct uvc_format instance with
> the fcc field set to 0. Since commit 50459f103edf ("media: uvcvideo:
> Remove format descriptions"), the driver relies on the V4L2 core to
> provide the format description string, which the V4L2 core can't do
> without a valid 4CC. This triggers a WARN_ON.
>
> As a format with a zero 4CC can't be selected, it is unusable for
> applications. Ignore the format completely without creating a uvc_format
> instance, which fixes the warning.
>
> Fixes: 50459f103edf ("media: uvcvideo: Remove format descriptions")
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index de64c9d789fd..25b8199f4e82 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -251,14 +251,17 @@ static int uvc_parse_format(struct uvc_device *dev,
>                 /* Find the format descriptor from its GUID. */
>                 fmtdesc = uvc_format_by_guid(&buffer[5]);
>
> -               if (fmtdesc != NULL) {
> -                       format->fcc = fmtdesc->fcc;
> -               } else {
> +               if (!fmtdesc) {
> +                       /*
> +                        * Unknown video formats are not fatal errors, the
> +                        * caller will skip this descriptor.
> +                        */
>                         dev_info(&streaming->intf->dev,
>                                  "Unknown video format %pUl\n", &buffer[5]);
> -                       format->fcc = 0;
> +                       return 0;
>                 }
>
> +               format->fcc = fmtdesc->fcc;
>                 format->bpp = buffer[21];
>
>                 /*
> @@ -689,6 +692,8 @@ static int uvc_parse_streaming(struct uvc_device *dev,
>                                 &interval, buffer, buflen);


For devices with unknown formats streaming->nformats will not be
valid, it will be higher than the actual formats on
streaming->formats.

>                         if (ret < 0)
>                                 goto error;
> +                       if (!ret)
> +                               break;
>
>                         frame += format->nframes;
>                         format++;
> --
> Regards,
>
> Laurent Pinchart
>
Laurent Pinchart May 1, 2023, 12:01 p.m. UTC | #2
Hi Ricardo,

On Mon, May 01, 2023 at 01:44:11PM +0200, Ricardo Ribalda wrote:
> Hi Laurent
> 
> I agree with the intent of the patch but am not sure that this will work.
> 
> Regards!
> 
> On Thu, 20 Apr 2023 at 12:07, Laurent Pinchart wrote:
> >
> > When the uvcvideo driver encounters a format descriptor with an unknown
> > format GUID, it creates a corresponding struct uvc_format instance with
> > the fcc field set to 0. Since commit 50459f103edf ("media: uvcvideo:
> > Remove format descriptions"), the driver relies on the V4L2 core to
> > provide the format description string, which the V4L2 core can't do
> > without a valid 4CC. This triggers a WARN_ON.
> >
> > As a format with a zero 4CC can't be selected, it is unusable for
> > applications. Ignore the format completely without creating a uvc_format
> > instance, which fixes the warning.
> >
> > Fixes: 50459f103edf ("media: uvcvideo: Remove format descriptions")
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > ---
> >  drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++----
> >  1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > index de64c9d789fd..25b8199f4e82 100644
> > --- a/drivers/media/usb/uvc/uvc_driver.c
> > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > @@ -251,14 +251,17 @@ static int uvc_parse_format(struct uvc_device *dev,
> >                 /* Find the format descriptor from its GUID. */
> >                 fmtdesc = uvc_format_by_guid(&buffer[5]);
> >
> > -               if (fmtdesc != NULL) {
> > -                       format->fcc = fmtdesc->fcc;
> > -               } else {
> > +               if (!fmtdesc) {
> > +                       /*
> > +                        * Unknown video formats are not fatal errors, the
> > +                        * caller will skip this descriptor.
> > +                        */
> >                         dev_info(&streaming->intf->dev,
> >                                  "Unknown video format %pUl\n", &buffer[5]);
> > -                       format->fcc = 0;
> > +                       return 0;
> >                 }
> >
> > +               format->fcc = fmtdesc->fcc;
> >                 format->bpp = buffer[21];
> >
> >                 /*
> > @@ -689,6 +692,8 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> >                                 &interval, buffer, buflen);
> 
> For devices with unknown formats streaming->nformats will not be
> valid, it will be higher than the actual formats on
> streaming->formats.

Indeed. I think this could be handled quite simply:

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index d966d003632b..cc6608eb3ab9 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -679,7 +679,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
 	interval = (u32 *)&frame[nframes];

 	streaming->formats = format;
-	streaming->nformats = nformats;
+	streaming->nformats = 0;

 	/* Parse the format descriptors. */
 	while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE) {
@@ -695,6 +695,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
 			if (!ret)
 				break;

+			streaming->nformats++;
 			frame += format->nframes;
 			format++;

What do you think ? I can submit a v2 with this change.

> >                         if (ret < 0)
> >                                 goto error;
> > +                       if (!ret)
> > +                               break;
> >
> >                         frame += format->nframes;
> >                         format++;
Ricardo Ribalda May 1, 2023, 1:22 p.m. UTC | #3
Hi Laurent

On Mon, 1 May 2023 at 14:01, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> On Mon, May 01, 2023 at 01:44:11PM +0200, Ricardo Ribalda wrote:
> > Hi Laurent
> >
> > I agree with the intent of the patch but am not sure that this will work.
> >
> > Regards!
> >
> > On Thu, 20 Apr 2023 at 12:07, Laurent Pinchart wrote:
> > >
> > > When the uvcvideo driver encounters a format descriptor with an unknown
> > > format GUID, it creates a corresponding struct uvc_format instance with
> > > the fcc field set to 0. Since commit 50459f103edf ("media: uvcvideo:
> > > Remove format descriptions"), the driver relies on the V4L2 core to
> > > provide the format description string, which the V4L2 core can't do
> > > without a valid 4CC. This triggers a WARN_ON.
> > >
> > > As a format with a zero 4CC can't be selected, it is unusable for
> > > applications. Ignore the format completely without creating a uvc_format
> > > instance, which fixes the warning.
> > >
> > > Fixes: 50459f103edf ("media: uvcvideo: Remove format descriptions")
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > ---
> > >  drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++----
> > >  1 file changed, 9 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > > index de64c9d789fd..25b8199f4e82 100644
> > > --- a/drivers/media/usb/uvc/uvc_driver.c
> > > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > > @@ -251,14 +251,17 @@ static int uvc_parse_format(struct uvc_device *dev,
> > >                 /* Find the format descriptor from its GUID. */
> > >                 fmtdesc = uvc_format_by_guid(&buffer[5]);
> > >
> > > -               if (fmtdesc != NULL) {
> > > -                       format->fcc = fmtdesc->fcc;
> > > -               } else {
> > > +               if (!fmtdesc) {
> > > +                       /*
> > > +                        * Unknown video formats are not fatal errors, the
> > > +                        * caller will skip this descriptor.
> > > +                        */
> > >                         dev_info(&streaming->intf->dev,
> > >                                  "Unknown video format %pUl\n", &buffer[5]);
> > > -                       format->fcc = 0;
> > > +                       return 0;
> > >                 }
> > >
> > > +               format->fcc = fmtdesc->fcc;
> > >                 format->bpp = buffer[21];
> > >
> > >                 /*
> > > @@ -689,6 +692,8 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> > >                                 &interval, buffer, buflen);
> >
> > For devices with unknown formats streaming->nformats will not be
> > valid, it will be higher than the actual formats on
> > streaming->formats.
>
> Indeed. I think this could be handled quite simply:

We will still be overallocating. I guess it is not a big deal...

But what about a helper function.  I think it will be less hacky


diff --git a/drivers/media/usb/uvc/uvc_driver.c
b/drivers/media/usb/uvc/uvc_driver.c
index 7aefa76a42b3..b49c2b911d03 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -483,6 +483,33 @@ static int uvc_parse_format(struct uvc_device *dev,
        return buffer - start;
 }

+static bool is_valid_format(unsigned char *buffer, unsigned int buflen)
+{
+       if (buflen < 2)
+               return false;
+
+       switch (buffer[2]) {
+       case UVC_VS_FORMAT_UNCOMPRESSED:
+       case UVC_VS_FORMAT_MJPEG:
+       case UVC_VS_FORMAT_DV:
+       case UVC_VS_FORMAT_FRAME_BASED:
+       {
+               const struct uvc_format_desc *fmtdesc;
+
+               if (buflen < 6)
+                       return false;
+               fmtdesc = uvc_format_by_guid(&buffer[5]);
+               if (!fmtdesc)
+                       return false;
+               return true;
+       }
+       default:
+               break;
+       }
+
+       return false;
+}
+
 static int uvc_parse_streaming(struct uvc_device *dev,
        struct usb_interface *intf)
 {
@@ -613,19 +640,15 @@ static int uvc_parse_streaming(struct uvc_device *dev,

        /* Count the format and frame descriptors. */
        while (_buflen > 2 && _buffer[1] == USB_DT_CS_INTERFACE) {
-               switch (_buffer[2]) {
-               case UVC_VS_FORMAT_UNCOMPRESSED:
-               case UVC_VS_FORMAT_MJPEG:
-               case UVC_VS_FORMAT_FRAME_BASED:
+               if (is_valid_format(_buffer, _buflen))
                        nformats++;
-                       break;

+               switch (_buffer[2]) {
                case UVC_VS_FORMAT_DV:
                        /*
                         * DV format has no frame descriptor. We will create a
                         * dummy frame descriptor with a dummy frame interval.
                         */
-                       nformats++;
                        nframes++;
                        nintervals++;
                        break;
@@ -679,11 +702,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,

        /* Parse the format descriptors. */
        while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE) {
-               switch (buffer[2]) {
-               case UVC_VS_FORMAT_UNCOMPRESSED:
-               case UVC_VS_FORMAT_MJPEG:
-               case UVC_VS_FORMAT_DV:
-               case UVC_VS_FORMAT_FRAME_BASED:
+               if (!is_valid_format(buffer, buflen)) {
                        format->frame = frame;
                        ret = uvc_parse_format(dev, streaming, format,
                                &interval, buffer, buflen);
@@ -692,13 +711,6 @@ static int uvc_parse_streaming(struct uvc_device *dev,

                        frame += format->nframes;
                        format++;
-
-                       buflen -= ret;
-                       buffer += ret;
-                       continue;
-
-               default:
-                       break;
                }

                buflen -= buffer[0];


>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index d966d003632b..cc6608eb3ab9 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -679,7 +679,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
>         interval = (u32 *)&frame[nframes];
>
>         streaming->formats = format;
> -       streaming->nformats = nformats;
> +       streaming->nformats = 0;
>
>         /* Parse the format descriptors. */
>         while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE) {
> @@ -695,6 +695,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
>                         if (!ret)
>                                 break;
>
> +                       streaming->nformats++;
>                         frame += format->nframes;
>                         format++;
>
> What do you think ? I can submit a v2 with this change.
>
> > >                         if (ret < 0)
> > >                                 goto error;
> > > +                       if (!ret)
> > > +                               break;
> > >
> > >                         frame += format->nframes;
> > >                         format++;
>
> --
> Regards,
>
> Laurent Pinchart



--
Ricardo Ribalda
Laurent Pinchart May 6, 2023, 7:08 a.m. UTC | #4
Hi Ricardo,

On Mon, May 01, 2023 at 03:22:16PM +0200, Ricardo Ribalda wrote:
> On Mon, 1 May 2023 at 14:01, Laurent Pinchart wrote:
> > On Mon, May 01, 2023 at 01:44:11PM +0200, Ricardo Ribalda wrote:
> > > Hi Laurent
> > >
> > > I agree with the intent of the patch but am not sure that this will work.
> > >
> > > Regards!
> > >
> > > On Thu, 20 Apr 2023 at 12:07, Laurent Pinchart wrote:
> > > >
> > > > When the uvcvideo driver encounters a format descriptor with an unknown
> > > > format GUID, it creates a corresponding struct uvc_format instance with
> > > > the fcc field set to 0. Since commit 50459f103edf ("media: uvcvideo:
> > > > Remove format descriptions"), the driver relies on the V4L2 core to
> > > > provide the format description string, which the V4L2 core can't do
> > > > without a valid 4CC. This triggers a WARN_ON.
> > > >
> > > > As a format with a zero 4CC can't be selected, it is unusable for
> > > > applications. Ignore the format completely without creating a uvc_format
> > > > instance, which fixes the warning.
> > > >
> > > > Fixes: 50459f103edf ("media: uvcvideo: Remove format descriptions")
> > > > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > ---
> > > >  drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++----
> > > >  1 file changed, 9 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > > > index de64c9d789fd..25b8199f4e82 100644
> > > > --- a/drivers/media/usb/uvc/uvc_driver.c
> > > > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > > > @@ -251,14 +251,17 @@ static int uvc_parse_format(struct uvc_device *dev,
> > > >                 /* Find the format descriptor from its GUID. */
> > > >                 fmtdesc = uvc_format_by_guid(&buffer[5]);
> > > >
> > > > -               if (fmtdesc != NULL) {
> > > > -                       format->fcc = fmtdesc->fcc;
> > > > -               } else {
> > > > +               if (!fmtdesc) {
> > > > +                       /*
> > > > +                        * Unknown video formats are not fatal errors, the
> > > > +                        * caller will skip this descriptor.
> > > > +                        */
> > > >                         dev_info(&streaming->intf->dev,
> > > >                                  "Unknown video format %pUl\n", &buffer[5]);
> > > > -                       format->fcc = 0;
> > > > +                       return 0;
> > > >                 }
> > > >
> > > > +               format->fcc = fmtdesc->fcc;
> > > >                 format->bpp = buffer[21];
> > > >
> > > >                 /*
> > > > @@ -689,6 +692,8 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> > > >                                 &interval, buffer, buflen);
> > >
> > > For devices with unknown formats streaming->nformats will not be
> > > valid, it will be higher than the actual formats on
> > > streaming->formats.
> >
> > Indeed. I think this could be handled quite simply:
> 
> We will still be overallocating. I guess it is not a big deal...
> 
> But what about a helper function.  I think it will be less hacky
> 
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c
> b/drivers/media/usb/uvc/uvc_driver.c
> index 7aefa76a42b3..b49c2b911d03 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -483,6 +483,33 @@ static int uvc_parse_format(struct uvc_device *dev,
>         return buffer - start;
>  }
> 
> +static bool is_valid_format(unsigned char *buffer, unsigned int buflen)
> +{
> +       if (buflen < 2)
> +               return false;
> +
> +       switch (buffer[2]) {
> +       case UVC_VS_FORMAT_UNCOMPRESSED:
> +       case UVC_VS_FORMAT_MJPEG:
> +       case UVC_VS_FORMAT_DV:
> +       case UVC_VS_FORMAT_FRAME_BASED:
> +       {
> +               const struct uvc_format_desc *fmtdesc;
> +
> +               if (buflen < 6)

Not the right length.

> +                       return false;
> +               fmtdesc = uvc_format_by_guid(&buffer[5]);

This isn't quite right for MJPEG and DV.

Honestly, I'm not sure I would bother. We're overallocating only for
devices that expose non-supported formats. That's a very small minority
of devices, the extra memory is quite small, and we should instead add
support for those formats anyway.

> +               if (!fmtdesc)
> +                       return false;
> +               return true;
> +       }
> +       default:
> +               break;
> +       }
> +
> +       return false;
> +}
> +
>  static int uvc_parse_streaming(struct uvc_device *dev,
>         struct usb_interface *intf)
>  {
> @@ -613,19 +640,15 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> 
>         /* Count the format and frame descriptors. */
>         while (_buflen > 2 && _buffer[1] == USB_DT_CS_INTERFACE) {
> -               switch (_buffer[2]) {
> -               case UVC_VS_FORMAT_UNCOMPRESSED:
> -               case UVC_VS_FORMAT_MJPEG:
> -               case UVC_VS_FORMAT_FRAME_BASED:
> +               if (is_valid_format(_buffer, _buflen))
>                         nformats++;
> -                       break;
> 
> +               switch (_buffer[2]) {
>                 case UVC_VS_FORMAT_DV:
>                         /*
>                          * DV format has no frame descriptor. We will create a
>                          * dummy frame descriptor with a dummy frame interval.
>                          */
> -                       nformats++;
>                         nframes++;
>                         nintervals++;
>                         break;
> @@ -679,11 +702,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> 
>         /* Parse the format descriptors. */
>         while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE) {
> -               switch (buffer[2]) {
> -               case UVC_VS_FORMAT_UNCOMPRESSED:
> -               case UVC_VS_FORMAT_MJPEG:
> -               case UVC_VS_FORMAT_DV:
> -               case UVC_VS_FORMAT_FRAME_BASED:
> +               if (!is_valid_format(buffer, buflen)) {
>                         format->frame = frame;
>                         ret = uvc_parse_format(dev, streaming, format,
>                                 &interval, buffer, buflen);
> @@ -692,13 +711,6 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> 
>                         frame += format->nframes;
>                         format++;
> -
> -                       buflen -= ret;
> -                       buffer += ret;
> -                       continue;
> -
> -               default:
> -                       break;
>                 }
> 
>                 buflen -= buffer[0];
> 
> > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > index d966d003632b..cc6608eb3ab9 100644
> > --- a/drivers/media/usb/uvc/uvc_driver.c
> > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > @@ -679,7 +679,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> >         interval = (u32 *)&frame[nframes];
> >
> >         streaming->formats = format;
> > -       streaming->nformats = nformats;
> > +       streaming->nformats = 0;
> >
> >         /* Parse the format descriptors. */
> >         while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE) {
> > @@ -695,6 +695,7 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> >                         if (!ret)
> >                                 break;
> >
> > +                       streaming->nformats++;
> >                         frame += format->nframes;
> >                         format++;
> >
> > What do you think ? I can submit a v2 with this change.
> >
> > > >                         if (ret < 0)
> > > >                                 goto error;
> > > > +                       if (!ret)
> > > > +                               break;
> > > >
> > > >                         frame += format->nframes;
> > > >                         format++;
diff mbox series

Patch

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index de64c9d789fd..25b8199f4e82 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -251,14 +251,17 @@  static int uvc_parse_format(struct uvc_device *dev,
 		/* Find the format descriptor from its GUID. */
 		fmtdesc = uvc_format_by_guid(&buffer[5]);
 
-		if (fmtdesc != NULL) {
-			format->fcc = fmtdesc->fcc;
-		} else {
+		if (!fmtdesc) {
+			/*
+			 * Unknown video formats are not fatal errors, the
+			 * caller will skip this descriptor.
+			 */
 			dev_info(&streaming->intf->dev,
 				 "Unknown video format %pUl\n", &buffer[5]);
-			format->fcc = 0;
+			return 0;
 		}
 
+		format->fcc = fmtdesc->fcc;
 		format->bpp = buffer[21];
 
 		/*
@@ -689,6 +692,8 @@  static int uvc_parse_streaming(struct uvc_device *dev,
 				&interval, buffer, buflen);
 			if (ret < 0)
 				goto error;
+			if (!ret)
+				break;
 
 			frame += format->nframes;
 			format++;