PR #24291 opened by Diego de Souza (ddesouza) URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24291 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24291.patch
A hardware -hwaccel_output_format was treated as a preference: get_format() settled for another hardware format of the same device type when the requested one was unavailable. CUDA and CUARRAY share a device type, so this is reachable in practice. The frames were then unusable. hwaccel_retrieve_data() asked av_hwframe_transfer_data() for the requested format, but the destination frame carries no frames context, so the transfer took the allocating path and failed on a hardware format. No frames were emitted at all. Substituting is not desirable even where the frames would be usable: the option exists so that the rest of the pipeline can rely on receiving a specific format, and quietly producing a different one defeats that. Treat a hardware -hwaccel_output_format as a constraint on format selection and fall back to software decoding when it cannot be satisfied, as already happens when an hwaccel cannot be set up at all. A software -hwaccel_output_format still only requests a download. >From 9aa2cb15b9115d41f5befd9165a49c8233f4ff5d Mon Sep 17 00:00:00 2001 From: Diego de Souza <[email protected]> Date: Tue, 25 Aug 2026 18:04:52 +0200 Subject: [PATCH] fftools/ffmpeg_dec: do not substitute a different hardware format A hardware -hwaccel_output_format was treated as a preference: get_format() settled for another hardware format of the same device type when the requested one was unavailable. CUDA and CUARRAY share a device type, so this is reachable in practice. The frames were then unusable. hwaccel_retrieve_data() asked av_hwframe_transfer_data() for the requested format, but the destination frame carries no frames context, so the transfer took the allocating path and failed on a hardware format. No frames were emitted at all. Substituting is not desirable even where the frames would be usable: the option exists so that the rest of the pipeline can rely on receiving a specific format, and quietly producing a different one defeats that. Treat a hardware -hwaccel_output_format as a constraint on format selection and fall back to software decoding when it cannot be satisfied, as already happens when an hwaccel cannot be set up at all. A software -hwaccel_output_format still only requests a download. Signed-off-by: Diego de Souza <[email protected]> --- fftools/ffmpeg_dec.c | 41 ++++++++++++++++++++--------------------- 1 file changed, 20 insertions(+), 21 deletions(-) diff --git a/fftools/ffmpeg_dec.c b/fftools/ffmpeg_dec.c index 1498afa880..5e7467797b 100644 --- a/fftools/ffmpeg_dec.c +++ b/fftools/ffmpeg_dec.c @@ -1314,6 +1314,7 @@ static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat { DecoderPriv *dp = s->opaque; const enum AVPixelFormat *p; + int hwaccel_output_is_hw; int ret; ret = multiview_setup(dp, s); @@ -1325,6 +1326,14 @@ static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat dp->hwaccel_pix_fmt = AV_PIX_FMT_NONE; + /* A hardware hwaccel_output_format constrains which hardware format may + * be selected, rather than requesting a conversion: frames are not + * implicitly transferred between two hardware formats. A software one + * only asks for a download and imposes no such constraint. */ + hwaccel_output_is_hw = dp->hwaccel_output_format != AV_PIX_FMT_NONE && + (av_pix_fmt_desc_get(dp->hwaccel_output_format)->flags & + AV_PIX_FMT_FLAG_HWACCEL); + for (p = pix_fmts; *p != AV_PIX_FMT_NONE; p++) { const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p); const AVCodecHWConfig *config = NULL; @@ -1332,6 +1341,9 @@ static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL)) break; + if (hwaccel_output_is_hw && *p != dp->hwaccel_output_format) + continue; + if (dp->hwaccel_id == HWACCEL_GENERIC || dp->hwaccel_id == HWACCEL_AUTO) { for (int i = 0;; i++) { @@ -1347,31 +1359,18 @@ static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat } if (config && config->device_type == dp->hwaccel_device_type) { dp->hwaccel_pix_fmt = *p; - /* Stop at the first matching hardware format unless the user - * explicitly requested a different *hardware* output format - * (e.g. CUARRAY vs CUDA, which share a device type) - in that - * case keep scanning for the exact match. A software - * hwaccel_output_format requests a download and imposes no such - * preference, so it must not switch us off the default (first) - * hardware format. */ - if (dp->hwaccel_output_format == AV_PIX_FMT_NONE || - dp->hwaccel_output_format == *p || - !(av_pix_fmt_desc_get(dp->hwaccel_output_format)->flags & AV_PIX_FMT_FLAG_HWACCEL)) - break; + break; } } - if (dp->hwaccel_pix_fmt != AV_PIX_FMT_NONE) { - if (dp->hwaccel_output_format != AV_PIX_FMT_NONE && - dp->hwaccel_output_format != dp->hwaccel_pix_fmt && - (av_pix_fmt_desc_get(dp->hwaccel_output_format)->flags & AV_PIX_FMT_FLAG_HWACCEL)) - av_log(dp, AV_LOG_WARNING, - "Requested hwaccel output format '%s' not available, " - "falling back to '%s'\n", - av_get_pix_fmt_name(dp->hwaccel_output_format), - av_get_pix_fmt_name(dp->hwaccel_pix_fmt)); + if (dp->hwaccel_pix_fmt != AV_PIX_FMT_NONE) return dp->hwaccel_pix_fmt; - } + + if (hwaccel_output_is_hw && *p != AV_PIX_FMT_NONE) + av_log(dp, AV_LOG_WARNING, + "Requested hwaccel output format '%s' is not available, " + "falling back to software decoding\n", + av_get_pix_fmt_name(dp->hwaccel_output_format)); return *p; } -- 2.52.0 _______________________________________________ ffmpeg-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
